There often comes a moment, talking to staff at Transform, when they feel the need to point out - because you didn't ask - that they have been Transformed themselves. It happens with Lindsay Mullins, the 43-year-old who handles Transform's PR and tackles complaints from patients, when we are talking about the why of cosmetic surgery: why increasing numbers of whole, healthy people in Britain are submitting themselves to surgery to alter their appearance.

"I've had surgery," she says. "There comes a point when something bothers people enough that it affects the way they live their lives every day, and that's the time they have cosmetic surgery. Most don't have it to be ultra-glamorous. The average person has it to feel normal. To have what society perceives as a normal-sized nose or bust."

I look at Mullins sitting behind her desk, a neat, bright woman in a black top, with pale blond hair. There is nothing about her nose or bust which screams either abnormal, or fixed. I want to ask, but there are dangers in guessing the wrong operation. Later in the day in Transform's sprawling national empire of alteration it will seem natural to ask a question such as "What is it you had done?" but it is still early.

A few minutes later she gives me the answer anyway, while I'm puzzling over one of a pile of testimonials to the wonder of rhinoplasty - a nose job. "I always hated my nose, too long and crooked, very self-conscious in profile," wrote the patient. "Now it's great - don't mind sitting at traffic lights/junctions in the car." "I know exactly how she felt," says Mullins. She, too, had loathed moments when her car sat at the lights and, she believed, her nose in profile became an object of fascination and mockery to the people in the car next to her. She'd turned her head away. Then she had her nose done. The price for a rhinoplasty at Transform is £3,000, but staff get a discount.

"It would be lovely if we lived in a utopia where everybody accepted everyone, but we don't," says Mullins. "Whether we like it or not, we live in a society where survey after survey has proven that if you're better looking you'll get on better in your job."

Business is humming along nicely at Transform, despite the storm of hostile media coverage in August when the General Medical Council struck off a former Transform doctor, Thomas Norton, for serious professional misconduct. A former morphine addict with a conviction for glassing a man in a pub, Norton's misdemeanours included failing to anaesthetise a woman properly during an operation to transfer fat from her waist and hips to her breast and thighs. She woke to hear Norton crying: "Christ, get her back under!"

The barrage of criticism of Transform, led by surgeons from professional bodies who mix NHS work and private practice, doesn't seem to have hurt the company much, and not just because Norton stopped working there in the early 1990s. The demand is too great, and the seekers after transformation from too diverse a social background. Britons now spend £180m a year on cosmetic surgery, 400% more than a decade ago.

Amid the furore over the Norton case, few asked the question why his patients, of their own volition, had chosen to submit themselves to expensive, medically unnecessary ordeals which can involve weeks in bandages and follow-up surgery. "It's really strange that in the last two weeks of the Norton thing, certainly during and immediately after his case, there was absolutely no effect on business," says John Pickering, Transform's clinical director, eating a biscuit in one of the firm's set of tiny, boxy offices in Hale Barns outside Manchester.

Transform is owned by John Ryan, who started out as salesman in the firm in the 70s and gradually bought up the shares. Among his other business interests, he owns Doncaster football club. Transform has three operating centres, in Newcastle, London and Bowdon in Cheshire, plus clinics - or salesrooms, as its critics would call them - in Glasgow, Newcastle, Leeds, Manchester, Sheffield, Nottingham, Birmingham, Bristol, London, Southampton and Brighton. Transform has brought cosmetic surgery to the masses. "In terms of our patients, the majority are people from the estates," says Pickering. "Very occasionally you'll get the rich and famous. You'd be amazed how many people pay in cash."

Anna Cartwright, the marketing manager, shows how Transform's ads have moved away from "before" and "after" shots to what she argues is a subtle, more open-ended approach. It isn't that subtle, though. "We've been creating beautiful bodies for over 25 years," runs one ad. "Breast enlargement from £62 per month, fat removal from £50 per month, nose reshaping from £53 per month, wrinkle treatments from £25 per month. Dial 4 A Loan."

Dial 4 A Loan is the finance company which Transform suggests patients apply to if they can't afford the thousands of pounds needed for surgical procedures. "All this credit message is doing is making people realise that this is affordable," explains Cartwright. Unprompted, in mid-spiel, she points out her own Transformation. "I had liposuction and it changed my figure drastically. All my life I've been hiding my bottom half and now I'm in proportion. I'm not going to have skinny legs, I'm not going to have fantastic legs, but I'm in proportion, and I fit in. So what we're trying to say through the advertising is you can fit in. If you're uncomfortable, we can help. I was born with that typical pear shape, so it wasn't to do with exercise, and with the lipo it managed to get me in proportion, so now I don't feel that everyone's looking at me, I don't feel like I'm sticking out of the crowd."

Last year Transform carried out 5,570 operations and about 7,000 non-surgical procedures such as anti-wrinkle injections. This year, it has had about 150 complaints. Mullins showed me a few. "I've been very displeased with my surgery, because I feel it's not made much difference to my appearance," wrote one rhinoplasty patient.

Somehow the complaints were reassuring; it was the testimonials which were unsettling. "My nose didn't bother me until I separated from a long-standing partner. I looked in the mirror one day and decided that it was time to make inquiries. I contacted Transform," wrote one recipient of surgery, apparently delighted with the result. "Being self-conscious in public is a frustrating and annoying condition, the chance to be normal did not need a lot of thought," said another. A third, writing in block capitals: "I felt I was always 2nd class to everybody else, and that everybody made fun of how I looked... now I have genuine confidence."

I drive with Pickering to Bowdon. The operating centre, two semi-detached houses knocked together, stands in a prosperous area of Cheshire favoured by wealthy footballers. "Just a few years ago they were doing four breast augmentations a fortnight here," says Pickering. "Now we're operating seven days a week, 10 hours a day, so you can see the demand is growing. People have accused Transform of creating a demand. You can't create a demand like that. The demand is already there."

Roy Saleh, a doctor who carries out non-surgical cosmetic procedures, sits in a grey padded chair, like a dentist's chair, in the middle of the large, strangely bare room where he works, and talks of the battle to lower patient expectations. "Very often you'll have them sitting in the chair and they'll say, 'Well, I thought of waiting a couple of years and then I'm going to have the big job.' And what they imagine is that they'll be put to sleep and a magic wand will be wafted over them and the big job will get rid of everything. When you ask them what they mean by 'the big job', they say, 'I'll have a facelift, and everything else will be all right.' And you say, 'Well, it won't affect your nose, it won't affect your eyes, it won't affect your forehead...' There's a lack of knowledge, a lack of understanding, and it's up to us to educate them."

At around lunchtime, an 18-year-old leaves the clinic with her boyfriend. She is slim and very pretty, in a blue tracksuit; she's from Liverpool, she's just done her A-levels, and she's taking a year out before applying to university. She's clever and quite clear about what she's doing. In August, she had bags of silicone gel surgically inserted into her breasts at Bowdon. It cost £3,500, from her savings from her job, and with help from her parents.

"None of my friends and family wanted me to have it done," she says. "I wasn't pressured at all. I've never been bullied or teased or anything. It was just a decision I made on my own. I haven't even gone big; just gone to a comfortable size for myself. It was just for me. It was just for my own confidence." A few years ago Transform set 18 as the minimum age for patients. She first contacted them in July. "They did say maybe I should go away and think about it more. They said I should talk about it with my parents. They weren't trying to sell me something."

Transform was happy to do the operation, though. "I liked the surgeon. He was very sensitive and understanding," she says. "When I'd had it done, they shoved me out a bit. It was very much in and out. I was a bit worried a couple of days afterwards. They were understanding about that." And the couple walked off across the drizzly car park. Because she is so young, she will probably have to have the implants renewed in later life, which means a fresh operation. She knows it, yet she went ahead.

We drive south towards Nottingham. Pickering, a forthright Geordie who worked as an NHS nurse before joining Transform, lays into what he sees as the snobbish southern world of establishment cosmetic surgeons - NHS consultants who do private work on the side and who seldom miss an opportunity to criticise the mass market approach of their northern rivals.

"They don't do it all the time. They dabble in it at weekends. It's the way they pay for their extras in life. Breast augmentation is boring, there's no doubt about it," he says. "We've got one guy, all he does is liposuction. That's all he's done for 10 years. Sorry, but he's got more experience than an NHS guy who only does two cases a month. I've seen professors of surgery you wouldn't let operate on your dog."

Transform Nottingham is in a cluster of handsome old red-brick buildings in Tollerton, outside the city. Christine Davies, the clinic manager, has a set of three breast implants of different sizes sitting on her desk. They look like large pastilles, translucent grey humps with a dull finish. I pick one up. Davies comes in and sees I've been fidgeting with the implants. "They're very natural, by the way," she says. "I have them myself. My other half couldn't tell the difference. He didn't know me before. I was a patient at Transform before I worked with them."

Davies argues that the cosmetic surgery boom is the result of the sheer amount of money swilling around in the economy and a desire on the part of women (it is still predominantly women, although male cosmetic surgery is also on the increase) to draw a line beyond which they are no longer prepared to make sacrifices for home and family. "Years ago it was a case of wanting to get a new kitchen, or TV, or video. The attitude of a lot of the new generation is, 'I've done my bit, I've got a house, I've had the children, this is for me now.'"

I ask whether she thinks the enthusiasm for body-piercing and tattooing is part of the same change in the national mood which has led to the increase in cosmetic surgery. She is appalled at the comparison. "Cosmetic surgery is an improvement or refinement of what you've got. I get women in who've had their tummy buttons pierced, their nipples pierced - I just cringe. To me, that's like mutilation."

Many cosmetic surgery patients only want to conform to their idea of an average person, but some want more. Everybody in Transform repeats, in some form, what Davies says about what cosmetic surgery cannot do: "It doesn't change your life. It doesn't take problems away." Yet they all know that this is exactly what patients hope it can do, and that is the hope they are encouraging. Hope is what it is partly about; a feeling that even if cosmetic surgery doesn't offer the certainty of ordinariness turned to beauty, old age turned to youth, or loneliness turned to love, it loads fate's dice a bit in your favour.

In the evening Azhar Aslam, a cosmetic surgeon who divides his time between Transform and his own private practice, gives me a lift back to London. "The basic belief system in the west at the moment is that you've got this life once, and you want to live it to the full," he says.

He reels off the three main reasons women have breast augmentation, the commonest type of cosmetic surgery. "The first group is young girls in their late teens and early 20s who say their breasts never developed. They waited, and waited, and they're under peer pressure and magazine pressure, and they are really under-confident. The second group is women in their 30s who have had children who they breast fed; they had nice breasts before but they have changed. Finally there are women in their 40s and 50s who have always wanted breast augmentation but haven't had enough money. Now everything's completed, their children have grown up, and they want to look good for themselves."

Aslam recalls patients who wanted more than general confidence and a new look for the mirror. "I have a patient who said to me, 'These are hard times. Everybody is fearful of redundancy, and I'm the oldest in my group. Every time they talk about redundancy, they look at me. I don't want to look so old."

He's seen drastic changes for the better in some of his patients after surgery, he says, from withdrawn gloom to shining warmth. Yet there are times when he is called upon to work on a place which his scalpel cannot reach. "I saw a lady last week, she was only 43, very decent, very nice, who's desperately in love with this man who's told her she doesn't look good any more. He's had a relationship with her, he's slept with her, and now he's told her that she's ugly. So she's come looking for some kind of 'improvement', but I can't do anything, because she hasn't got anything wrong with the structure of her face. So I spent 45 minutes with her, trying to say life was much more than being in love with this man, who was probably a worthless bastard anyway."