Thrifty Living: No, I don't want to dress like sienna, even if it is cheap

Spend thrift Janie comes round for a cup of tea, looking very pleased with herself. "Ever heard of the Sienna syndrome?" she asks, semi-rhetorically. I try to look as if I am very up to date. Trouble is, I can't immediately remember exactly who Sienna Miller is. Is she the one who was dumped by Jude Law for the nanny, or the one who was hooked mid-nanny, or the one who was seduced post-nanny, but later dumped just before the Olivier Awards? I think the problem is that she has one of those instantly forgettable faces, a bit like Dido.

So, no. I haven't heard about her syndrome, although it could be the making of her. After all, you have to be pretty special in order to have a real syndrome named after you (as Baron Munchausen might agree, were he still around).

"Sienna syndrome is the name given to people who want to look like a star. Actually, for those who want to look like Sienna Miller. But can't afford it," continues Janie happily. Is that all? So what's the cure? "Finding cheap ways of looking like her, of course."

I'm trying to get my head around wanting to look like someone whose looks I can't actually recall; in which case, why would you want to look like her in the first place? "All right, call it the Duffy syndrome if you like," says Janie, irritated. "Or the Kate syndrome, but without the help of Topshop."

OK, I get it. In another era it would have been known as good old-fashioned envy. Now, however, it is dressed up as a "syndrome". And not a very serious one either, as relief can be found via outlets such as asos.com, which guides you towards the Sienna look, the Posh look or the J-Lo look, or TK Maxx, which has such a plethora of slashed-price designer goods that should you suffer from a multitude of syndromes, you could look like one star in the morning, another in the afternoon and another at bed-time.

And yet, you have to be a bit of a devoted shopper to really deal with your syndrome. Asos.com has a whole range of rather chavvish stuff to avoid; and who has time for TK Maxx, unless you have an entire morning to "find your size and flick through" one of its cavernous stores?

As ever, the French seem to have found a voguish way around this. They have come up with a rather jolly website that purports to offer "private" sales of Sienna looky-likey designer goods at huge discounts, a little at a time. Brand Alley is its name. It was invented in France in 2005, and launched in the UK last month.

The idea is that Brand Alley operates as a sort of discounted e-boutique, with everything cut in price by 30 to 70 per cent. The site is billed as a vente privée, (meaning private sale, but a very chic one), under the banner of specific designer labels. The catch? Each vente privée only lasts three or four days, with about four different sales a week, each of which starts and finishes on different dates.

Chloé, D&G, Fendi and Elle Macpherson underwear are some of the brands that have already been flogged cheap on Brand Alley. Soon to come will be sales from Guess childrenswear, Nike iPod running accessories (in time for the London Marathon) and Gucci sunglasses (in time for the sunny weather, ha ha). The stuff on sale comes from excess manufacture on certain lines, and has been picked by Brand Alley's buyer. Everything is in authentic packaging, and there's an eight-day return and refund policy.

According to the press people, Brand Alley also acts as a "style concierge", as there's quite a limited choice. Each vente privée only has about 12 items on show, or at most, three pages. In Brand Alley's view, this signals exclusivity. In my view, this signals smart marketing, and should be the way all online fashion outlets operate. If a site is too enormous (net-a-porter.com), it just seems far too troublesome to venture into, and as for TK Maxx, forget it. I prefer living, rather than devoting my life to "finding my size and flicking through".

Once you sign up to Brand Alley, you are "invited" by email to every sale. This, of course, could be the end to any meaningful frugality, as Spendthrift Janie guiltily admits. "I've bought Diesel jeans and a gorgeous pair of Fendi sunglasses," she said. "But, at 70 per cent off, I sort of had to do it. And I am suffering from a syndrome, you know."