It's a busy street opposite Tesco on the wrong side of Hammersmith, and from the outside it seems to be a six-storey house. Inside, it's part salon, part surgery, part James Bond. Women sit before mirrors with stretches of scalp exposed, while 'technicians' and 'stylists' work away with mesh and paste and thread and spray.

Some people are screened away. There are bald heads everywhere, some real, some mannequins. On trolleys, chairs and mirrors are long, glossy tails waiting to be 'locked' to their owners. MTV plays and there's a snack bar (most clients are here all day).

On one floor, Cheryl Tweedy from Girls Aloud is having extensions attached. Beside her is a woman with alopecia, here to have her bare head covered. Though celebrities come to Lucinda Ellery wishing for 'bigger hair' - Jordan, Michelle from Liberty X, Mutya from the Sugababes - the majority of clients come simply wanting hair.

About 20 per cent are women with cancer who have had chemotherapy (ironically, Kylie had extensions here before her diagnosis), while others have trichotillomania (compulsive hair-pulling), alopecia areata (Gail Porter, a recent sufferer, has just been invited in) and female-pattern baldness. All these conditions are thought to be on the rise.

At Lucinda Ellery's, clients have instant access to a network of fellow sufferers and, if their GP is less than sympathetic, they can be referred to two GPs specialising in hair loss, as well as a clinical psychologist. Clients may be tested for iron and vitamin B deficiency, and offered HSN tablets - entirely herbal, imported from America, and the only ones Lucinda believes make any difference. Those with trichotillomania have a 24-hour helpline to ring when they get the urge to pull, a buddy system and a secure website. The jewel in Lucinda Ellery's crown, though, is the 'volumiser' treatment, in which hair is attached by a complex plaiting system. Once on, it's like any other head of hair. You sleep in it, swim and shower in it, and get split ends like everybody else.

The technique was developed 20 years ago by Lucinda Ellery herself, gorgeous and glam (think Ab Fab's Patsy and open-topped sports cars), who knows more than most what it is to be a woman without hair. At nine, after her father's death, her hair fell out and she spent most of her life in wigs.

'We were living in Africa and within eight weeks I'd lost everything. The home, my family, my school, my nanny, my animals, my friends,' she says. Ellery was taken back to the UK - her hair loss had already started, so her head was shaved on the boat - and put in a convent in Wales. She recalls using boot polish on her head and children moving away from her in church. At 15, she got her first wig.

'There are so many millions of ways that add up to why hair is so important to a woman,' she says. 'It's hugely powerful. Women were shaved as a punishment, tarred and feathered, they cut it off when they give it up for God. It is a symbol of fertility, virility, sexuality, longevity. It's got sexual connotations, social, financial, cultural - it's massive. So if you wake up with half your head on the pillow, it stops you dead. It feels pathetic, sobbing to your doctor, but how can you carry on? We all know a "bad-hair day". Try a "bad-hair life".'

Ellery's bad-hair life stretched into her mid-thirties, when she finally devised undetectable extensions, after being inspired by Daryl Hannah's waist-length mermaid hair in Splash. 'Until then, I spent every penny on wigs,' she says. 'I wore them 24 hours a day, 365 days a year - I don't think I got a decent night's sleep for 20 years. It was the little things. Not being able to go swimming, or out in the rain or the wind. Noticing every Timotei ad, standing in a queue feeling eyes boring into my head, worrying about my wig every time someone hugged me. Once, in Marks & Spencer's, my wig got caught on someone's bracelet. We were on the escalator, I was going down, she was going up. I was shaking, so shocked and traumatised, I couldn't go back to that shop for seven years.'

When Ellery started the business in her kitchen (she was then a head-hunter and mother of three), her clients came purely for glamour. After a couple of years, someone came with a bald patch. 'Until then, I'd never seen another woman with a bald patch,' she says. 'I'd never, ever talked about it. I remember my daughter saying, "I never knew you were bald!" I was so shocked at that word. I said, "Didn't you think it was strange that Mummy had 120 different wigs?"'

Now, her client profile has changed. They are getting younger and younger and balder and balder. Around 20 per cent of women in the UK now have clinically significant hair loss. Two-thirds have femalepattern balding, overall thinning caused by hormones, ageing and genetics, while the other third lose hair for other reasons, including alopecia areata, an auto-immune disease linked to stress, which can happen in patches or all at once. In some cases, the hair grows back, in others, it never does.

On top of this, there's temporary hair loss as a result of chemotherapy (both breast cancer and lung cancer are rising among women) and trichotillomania, which affects up to 3 per cent of the population. The term trichotillomania was first coined in 1889 by a French dermatologist who had noticed the compulsion in many of his patients. Within psychiatry, it is often grouped with other obsessive-compulsive disorders, and can come with eating disorders and selfharming. Like anorexia, hair-pulling is overwhelmingly female, thought to be triggered by puberty and typically develops in adolescence, sometimes following a trauma.

Though exact statistics don't exist, many experts believe more women are losing more hair. Dr Sarah Riley, a GP and one of Ellery's medical advisors, is one of them. 'Even my experience as a GP suggests this,' she says. 'In my surgery the other day, four women came in with female-pattern hair loss. I see at least one a week.'

Why would this be? Again, there are no clear answers. Some studies link it to yo-yo dieting, others to pollution and stress. 'I'm sure stress will come out as a contributory factor,' says Dr Riley. 'We all know that women nowadays are trying to fit a lot more in. They're trying to have jobs and be mothers and good members of the PTA and good wives. We're trying to do it all, and I'm sure that somewhere along the line that increases the stress hormones.'

While current medical treatments are patchy and inconsistent - many doctors have never heard of trichotillomania - some of Ellery's clients are lucky enough to see her on the NHS. For those that can't, it's expensive, averaging at about £1,500 a year. For this reason, Ellery and Dr Riley are launching the Hair Management Academy, which aims to offer the Ellery treatment as the last-stop NHS option for women with clinically significant hair loss. (The best such women can hope for now is a wig on the NHS, then they are left to get on with it.) Ellery's vision is to spread her service to a series of salons around the UK.

Until then, her treatment is limited to a lucky few. Many of these find that, when the daily horror of wigs and worry have been banished, their stress fades, the vicious circle is broken and their hair grows back. The others have a beautiful disguise. The letters in Ellery's office showhow grateful they are - though some could still break your heart. 'It's so strange waking up not having to decide whether to wear a hat or a wig,' says one. 'Thank you so much for giving me so much confidence - but not too much. I won't forget what I really look like.'

Carly Morrel
23, a student nurse from Sittingbourne, Kent, has alopecia areata

I've got almost no hair on my head, none on my arms, my eyebrows are going and so are my eyelashes - I used to think I'd be all right as long as I've got my eyelashes. Now I don't believe it will ever grow back anywhere. When it started, I was 17 and I'd only been with my boyfriend a couple of months. Clive's six years older than me and I really don't think a boy my age could have coped. Clive just didn't seem to care. There were days I sobbed and sobbed and said, 'Why are you still with me? Look at the state of me ...' But he stayed.

I don't know why it happened. I was doing A levels when I found a bald patch, the size of a 10p piece, right at the front. I don't think I was any more stressed by exams than anyone else. After A levels, I got pregnant and that was a rough time - but the alopecia had started by then. There's no trace of it in the family. Maybe it's just the way I'm supposed to be. I tried steroid tablets, which worked when I was on five a day, but each time I reduced the dose, my hair fell out again. Apparently they're not good for you - though I didn't care about the risks. I just wanted my hair while I was young. In the end, though, my doctor refused to give me any more. Then I had steroid injections into my scalp, five at a time, but that didn't do much.

By the time I was pregnant with our second daughter, Phoebe, there was nothing left to try and my hair came out really quickly. I was never offered advice or counselling. I was a young girl starting out and I was allowed one NHS wig and that was it. That wig was acrylic and so horrible, hot and stiff, I cried. You're always conscious of it. Once at a club, dancing on stage, a friend accidentally pulled it off.

Most of the time I wore baseball caps. I had to change my whole appearance so they would blend in. I wore tracksuit bottoms and sports tops. I hated it. I like nice jewellery, stuff that's in fashion. I used to love going shopping, but I soon stopped. I couldn't be bothered.

I felt horrible, unattractive and ashamed. Ashamed of myself and ashamed for Clive. People used to say things. Once, in Asda, a man asked, 'Have you had a brain operation?' Another time, in my local shop, the woman serving said, 'Who are you hiding from?' I asked what she meant and she said, 'You've got a wig on.'

The worst was at the bingo hall where I work. This woman in the queue laughed a big cackly laugh and yelled, 'Why are you wearing a wig?' I didn't go out of my house for three days after that.

Getting my volumiser at Lucinda's was one of the best days of my life. After having my kids, it has to come next. At my first appointment, I was crying and Lucinda was crying. She kept saying I had a beautiful face and didn't need to worry any more. When I got home, my friend Emma burst into tears. She said it was like looking at me when I was 15. Clive said I looked just like I did when we first met.

Last week, I went to my GP to try and get NHS funding, but he practically laughed in my face. He said no because it was a 'cosmetic procedure', so I asked why some people got breast implants and nose jobs on the NHS while I had no hair and got nothing. He said, 'How do you feel? I can see you're not depressed because you're smiling!' I nearly cried walking out of there.

I have to go back to Lucinda's every six weeks for adjustments, and it costs £150 each time. I'm £800 overdrawn and I'm a student working in a bingo hall so it can't be good, can it? But I'll go for the rest of my life if I have to. Why? To feel normal.

Claire Conroy
25, trainee solicitor from Liverpool, with trichotillomania

You know how some of your hairs are coarser than others? Those are the ones I'd be looking for. I could be revising, watching telly, driving my car - stuck in traffic jams it was chronic - and my hands would automatically go to my head. I'd find a hair and register that I wanted to pull it out.

Sometimes I'd debate with myself for as long as it took, getting more and more wound up - then I'd just do it. If I had to try and find one particular hair I knew was in there, I'd erase an area until I got it. With each hair, it's a tiny little sting. I like that feeling. Then fetching the hair, messing with it in my hand.

I've been told it started when I was three. My mum was having a miscarriage, so she'd been taken to hospital in an ambulance and I was in my aunt's car. She looked in the rear-view mirror and saw me pulling out chunks of hair. I think it stopped quite soon, then began again when I was around 10 and starting a new school. I clearly remember sitting at home and pulling out just one hair, then seeing the bulb and the root and feeling totally fascinated.

After that, it stopped and started. Once, at Brownies, a friend noticed a bald patch on top of my head. During GCSEs, I needed the grades to make the sixth form and the pulling got worse. It made little bald patches that I covered by rearranging my hair with sprays and clips. As the patches got bigger, I coloured them in with mascara. I honestly thought it was something only I did and I just couldn't understand why I couldn't stop.

I thought I was keeping it a secret but people probably knew something wasn't right - but they also knew not to talk about it. I'm good at making things no-go areas.

My dad died when I was 20, and from then on it was terrible. I had no hair at all on the top of my head. I always pulled from the top, and you never change your site. I did so much damage, it refused to grow back in a few patches. When your scalp becomes shiny, like the palm of your hands, you know hair won't grow there any more.

Most of the time I had to wear scarves, and I couldn't go anywhere at short notice. I never went swimming. I had a boyfriend at the time, and I'd always go to bed after him and get up before him. I couldn't use other people's pillows because the scalp colouring would stain it. All my life was spent thinking about them. Such a waste of time.

Even then, no one ever asked. My friends knew not to. My mum had always been exasperated that I wouldn't talk about it to her - I still won't - but three years ago, she read an article about Lucinda Ellery and we went down to see her together. It was so emotional. I was crying all that day which isn't like me at all. Lucinda came in like a little hurricane. She was absolutely lovely and introduced me to another girl who had it. Somebody else who knew. There was no explaining to be done, she just understood.

Now I go to Lucinda's every six weeks. The area I pulled from is completely covered, so I can't get to it. The barrier is hopefully breaking the habit - I haven't pulled for nearly three years, though the urge is still there.

It's so hard for people to understand. With alopecia, it's not your fault, but this is something I do to myself. It's an impulse I have absolutely no control over, but I do feel shame, guilt. I haven't told my boyfriend yet. I've only been with him for five months, but we're moving in together so I've got to do it. It'll probably explain a few things. Very early on, I told him I didn't like having my head touched, so he never did it again. I'm dead nervous. I might email him. Thank God for modern communication.

Joanna Patrick
44, An EC official living in Brussels, had breast cancer

My hair had started to thin before the cancer - but the shock of the diagnosis and then the treatment were the final kick in the teeth. My hair was so fine, you could see the outline of my scalp, and my hair just wasn't growing back the same. I had cancer 10 years ago - and the final treatment finished five years ago - but I'll never stop coming to Lucinda.

Once you're told you have cancer, you enter a new world that's suddenly separate from everybody else - no one can possibly understand what you're going through. When it happened to me, I was single, living in Luxembourg and hadn't been there long. I'd left a stressful job in London for a change of life and then my mother had died very suddenly.

I hardly knew anyone and my French was nowhere near as good as it is now - imagine finding a lump and trying to understand what's happening when you only understand 50 per cent of what's being said to you. I can still hear the noise of the radiotherapy machine. Everyone would leave the room just before the therapy began - the big reinforced door would shut behind them - and I'd think, 'Can I come too?' Now that's really being alone.

For me, losing my hair was far worse than losing 30 per cent of my breast, because who sees that? You can disguise a lumpectomy. You can shove hankies down your bra, or not wear anything too low cut. Your hair is the first thing anybody notices. For women, it should be her crowning glory - it's her sexuality, it's absolutely fundamental.

When my hair fell out, I looked like a pineapple. I'd put on loads of weight and had these tufts on the top of my head. I didn't realise it at the time, but my whole body posture was closing in. I constantly looked down and avoided eye contact. I had no self-esteem, I was a mess.

The effect Lucinda has had on my life has been phenomenal. From the moment I walked into her studio, it was absolutely understood that I wasn't just some silly, vain person. This wasn't about 'glamour', it went much deeper. Suddenly I went from having no hair to having the possibility of long, curly, straight, thick hair. That first time, we went for a thick, brown, shaggy look - luxurious with undertones of red. When I left, I couldn't stop looking at myself. I just felt so confident, I literally walked taller.

It sounds absurd, but having hair gave me the courage and strength to sort myself out. I did a university degree and got a first. I met my husband in a Brussels nightclub. He's 10 years younger than me, very caring, very loving. This Christmas, I finally feel confident enough to go back on the operating table and have reconstructive surgery on my breast. It has taken 10 years, but soon I'll have the hair and I'll have the breasts!

I fly back to London every six weeks to get the extensions fixed into place. It probably costs about £1,500 a year. What else could I get for that? Clothes? A couple of good holidays? My hair makes me feel good every day. It's indispensable - it moved me on, gave me back my life.

· For further information, call 020 8741 8224 or visit www.lucindaellery.com. For general advice and support on alopecia, call Alopecia UK on 020 8333 1661 or visit www.alopeciaonline.org.uk