"I love spending my mum's money on clothes..."

Every schoolgirl dreams of getting the princess treatment. But the new breed of sophisticated, big-spending 10-year-olds, or 'tweenagers', take makeovers and manicures in their stride. These girls don't borrow their mothers' nail polish, they've got their own.

Would you ladies like to choose a nail colour?'' asks the manicurist. The ladies would indeed, and they peer at the various colours on offer. Sophie picks this season's mauve, and Lucy goes for one with glitter in.

Would you ladies like to choose a nail colour?'' asks the manicurist. The ladies would indeed, and they peer at the various colours on offer. Sophie picks this season's mauve, and Lucy goes for one with glitter in.

''Pop your fingers in there'' says the manicurist, motioning to a bowl of soaking solution. Sophie obliges. ''I'll give you a bit of a file. You know when you file, you should only do it from one direction,'' she advises. Sophie admits she doesn't. But that's because her mum won't let her borrow her nailfile. Life can be tough for a 10-year-old.

While other children are still in their pyjamas watching Saturday morning TV, Sophie O'Mahony and Lucy Hough, also 10, both from south-east London, are being pampered at Britain's first beauty salon for children. For Lucy and Sophie are tweenagers - a new consumer group identified by marketing people as the latest big-spenders. Aged between 10 and 13, they are sophisticated, demanding and boast an ever-rising disposable income. According to a report by the market-research company Datamonitor, for the past five years, label-obsessed tweenagers have seen their pocket money rise by an average of five per cent to £3 a week.

One factor influencing their increased spending power is divorce. Some parents try to compensate for having split up the family by over-indulging their children. Parents working long hours may also try to lessen their guilt by getting their wallets and purses out. And couples who have children later on in life have more money to spend on their offspring.

For £22.95 - a snip considering some of their allowances - tweenage customers at Mini Kin, in north London's affluent Muswell Hill, can indulge in a "Princess Treatment", which comprises a hairdo, a make-over and a dash of perfume. The products are made for children. The nail polish peels off, and the make-up goes no further than lip gloss, glitter gel for the cheeks and eyelids, and glitter hair mascara.

"Is this your first manicure?" I enquire of Lucy, as she relaxes back into a chair, dressed in her favourite Gap and Fat Face labels. ''Oh no,'' she says. ''I had one in New York.''

Joanna Stone-Khan, 38, who owns the salon, and who is giving the girls their manicures, looks at her own nails and sighs. ''Don't look at mine,'' she tells the girls. ''I've got housewife fingernails.'' She peers closer at Lucy's. ''I wish I had nails like this. You probably paint your nails a lot more often than I get a chance to.'' Lucy is offered the magazine Girl Talk to read in between coats of nail polish. Her nose turns up ever so slightly. Lucy reads the more sophisticated Mizz. No doubt she will soon be buying the tweenage versions of Cosmopolitan, Elle and Vogue - CosmoGirl, Elle Girl and Teen Vogue - shortly to be launched in the UK. Advertisers in the first issue of Teen Vogue in America included Chanel, Ralph Lauren, Lancÿme and Versace. Tweenagers - too old to be children, but too young to be teenagers - are a marketing dream. They are sophisticated enough to put forward a compelling argument for having what they want, but not yet cynical enough to realise they are being targeted by advertisers. And their pestering power is legendary.

''I love spending my mum's money on clothes,'' admits Lucy, who is wearing denim pedal-pushers, wedged denim disco shoes, and a Fat Face fleece. ''I like dressing up in fancy clothes - little dresses and things - but not all the time. I get a lot of things from New Look.

''One time, we went into a shop on the Isle of Wight just for a look, and I came out with a whole new wardrobe. I've got a lot of clothes, enough really. But I've seen some trousers in Gap. They're white. I really like them. Am I going to get them, mum?''

Her mother Laura, 42, a literary agent who is married to a barrister, says no because of the colour. And pestering won't get Lucy any further, she says. ''It doesn't work with me. I just get cross.''

Carol Amoruso, the salon's hairdresser, is applying pink gloop containing tiny silver stars and moons onto Sophie's cheeks. ''She's got lovely cheekbones,'' coos Ms Amoruso. The 10-year-old is used to make-up. ''For my birthday I got a big pot of make-up, which I wore whenever I got a chance,'' says Sophie. ''I wear it outside the house, but not all the time. I have freckles and sometimes I don't look right with them, so I put powder on to cover them up. And my lips look all funny, and I put lipstick on. I like big black eyelashes so I wear mascara.

''But I got spots and I thought the make-up wasn't helping, so now I don't. I like to keep my skin clear.''

Her parents - a sugar trader and a part-time manager/trainer - give her £1 a week pocket money, which she is saving for the future so she can ''pay the bills and buy a house''.

Her parents also pay for her clothes. ''I like designer dresses with thin straps,'' she says. "Most of my clothes come from Monsoon.''

Ms Stone-Khan got the idea for opening a salon for children because her son found going to the hairdresser's a traumatic experience. ''Then I thought it would be fun for girls to have the works, like their mums do,'' she says. She rejects the criticism that children shouldn't be encouraged to beautify themselves. ''Little girls think about it anyway. I would like to meet a mum whose girl hasn't nicked her nail polish,'' she says. ''You can get high-heeled Gucci sandals in children's sizes, and apparently Madonna's daughter has a full manicure and pedicure.

"I don't think you can prevent little girls being interested in that aspect of life."

Yet her products are similar in price to those for adults. ''It's all been tested. It's not toy-shop stuff,'' she says. ''It's real make-up. We don't have eye shadow, and the colours are not too harsh. I don't want it to be too serious. I don't want to create little madams. Kids are beautiful already. This is more of a pampering experience than a beauty salon.''

Ms Amoruso applies a smear of strawberry-tinted lip gloss to Lucy's lips. The little girl is delighted with the result. ''That's such a lovely colour on you,'' the woman tells her.

Once their makeover is done, Sophie and Lucy - all glitter, bouffant hair and shiny lips - are offered a squirt of children's perfume. Sophie rubs her wrists together, but is swiftly advised not to. ''Always press your fragrance, so it doesn't destroy the notes,'' warns Ms Stone-Khan.

So what do the girls think of their new look? ''I think I look really nice. It's really professional, and it shows I can look better,'' says Sophie. Lucy is equally taken by the experience. ''Brilliant. It's amazing how I can change. I really like it.''

Lucy's mother is similarly charmed. ''They look absolutely gorgeous, and it's not too much,'' she says. ''They both look very natural, and very pretty. It's good for a special treat, and it's a really reasonable price. The women took their time, and made them feel special.''

And that, one supposes, is what every tweenager is seeking when they hand over their - or rather, their parents' - money.