Katy Guest: Give us what we want: clothes that fit and no fuchsia bras

If the sudden rise in Marks & Spencer's share price is any indication, the appointment of Kate Bostock as the store's new head of womenswear is going to have the lady shoppers of Middle England bursting out of their control-top knickers with unrestrained glee. After years of feeble sales and falling profits under increasingly desperate managers, the image of M&S as a Great British Institution is little more than an atavistic folk memory for most women. We've all heard the stories about the quality and the economy (and the rows and rows of comfy cotton knickers), but anyone who has fought through the wall of polyester static and attempted to buy anything in M&S recently knows the reality is a hopelessly different matter.

The decision at last to appoint a woman as head of womenswear is hardly radical. In fact, the reasons behind it should have been blindingly obvious for a while. One M&S deputy store manager I know was ticked off by her male manager for wearing a shade of nail varnish he considered "hardly suitable" for the shop floor. "This is actually our best-selling colour," she told him. "But I wouldn't expect you to know that."

The fact that Bostock has graduated from Marks's two main rivals, Asda and Next, also bodes well. Not for nothing have disappointed shoppers been leaving the elasticated trouser departments in droves and heading to other high street stores that sell low-priced basics (Asda, Primark), clothes made of, oh bliss, natural fibres (Warehouse, Gap) and fashionable womenswear (almost anywhere in preference to dear old frumpy M&S).

Hopeless optimists who visit Marks & Spencer now in search of a well-cut T-shirt or a decent pair of socks will be found roaming the aisles like crazed harpies in some outer circle of hell, muttering, "What kind of sad, colourblind freak do they imagine is going to buy those pink, orange and brown stripy trousers with the little dashes of green and why have they always sold out of the only sizes anyone might ever want to buy?"

I hope the stock of Marks & Spencer will be improved by the appointment of someone who might just shop there. But in case Ms Bostock hasn't got the hang of it, here are some ideas:

As women get fatter, they do not necessarily grow longer arms. Making clothes biggerin proportion instead of just increasing the overall size of the pattern, while more tricky, might mean clothes would actually fit.

There are more size 12 women among your customers than size 20. That's why you always have hundreds of size 20 clothes left to moulder on the sale rack, and never any 34Cs.

Websites like figleaves.com and Agent Provocateur sell thousands of items of underwear and do not charge for delivery. Telling M&S website customers who try to order from you that "unfortunately, an error has occurred" will get you nowhere.

Keep selling trousers in three lengths and, for once, don't be tempted to emulate Next, whose customers will tell you that trying on trousers in "long", "extra long" and "baby giraffe" is just undignified.

Women with large breasts want to buy pretty bras. Women with small breasts want to buy pretty bras. They all want to buy them in black. Not fuchsia. Not electric turquoise. Not green.

If you move your stock around every two hours, nobody can find anything to buy it.

Why sell dozens of pairs of beige trousers and no beige socks?

Even if you call it Per Una Due, teenagers know it's M&S. Why not sell clothes for women who do want to shop there?

There's no point stocking 1,000 pairs of hosiery if they're all identical.

There is nothing sexy about 100 per cent polyamide.

Good luck. The women of Britain are counting on you.