Yes, you shall go to the ball

It's party time. Between now and New Year's Eve, the usual dress codes go out of the window. Expect to see oversized Santas, flashing reindeer antlers, and revellers dressed in all sorts of ridiculous outfits wandering, drunk and confused, in town centres up and down the country. Party season is fashion's silly season (and you thought every season was silly). There are two options: fancy dresses, as in sexy bits of nothing designed to reveal as much bare flesh as possible; and fancy dress, as in gangsters and molls, vicars and tarts.

At The Contemporary Wardrobe in deepest, darkest Bloomsbury, London, there are solutions to every party-goer's problems. The place itself is something of a find - literally. It is in an old Horse Hospital, hidden away on a narrow street called Colonnade. Ring on the doorbell (best to make an appointment first) and you will be told to come downstairs into the cobbled basement. It's dark, chilly and damp, and you have to be careful you don't slip on the sloping floor that was designed for horses to trot down.

Heather greets you there and, depending on whether you are looking for a Seventies' outfit (and judging by demand, you probably will be), or a Fifties' ballgown, she will direct you to the right rail. The clothes are filed by date. And there are rails and rails, ranging from the Forties to the present day.

The Contemporary Ward-robe is the collection of costume designer Roger Burton. He has been in the business since the Sixties, and he has collected more clothes than he knows what to do with. He has turned his collection into a library for his own work - mainly supplying costumes for TV commercials - and for anyone else who wants to hire it out. The highlight of the collection is a range of original Westwood/McLaren punk pieces. These T-shirts and bondage wear are probably worth more than the rest of the collection put together. Unfortunately, it is not for hire.

What is for hire is a full-length gold military-style dress with epaulettes and all the trimmings; a pair of Seventies' loon-pants with matching platform boots and Superfly shirt, or a pair of furry moon boots. There are clothes for men and women, but be prepared to spend some time rummaging to find the outfit you've always fantasised about wearing.

Like The Contemporary Wardrobe, Angels & Bermans is a collection of clothes and costumes primarily designed to be hired out to the wardrobe departments of film and theatre companies. "We are absolutely inundated at the moment," said their spokesperson. "Seventies' outfits are always very popular. There are lots of James Bond parties at the moment, too."

Angels & Bermans is the obvious choice for society party-goers in need of a little fancy dress. There are four floors of stuff, ranging from the Romans and Greeks (people actually hire costumes for toga parties, rather than simply wrapping themselves in an old sheet) to Star Trek and Alien. Dangerous Liaisons and 18th century costumes are in great demand right now, too. Costume hire costs from pounds 60+VAT for a week.

Over in London's Spitalfields, Stagestruck Costume Company is doing a roaring trade. The phones don't stop ringing with requests to hire pieces, ranging from theatrical to vintage. There are also contemporary evening clothes, and a selection of masks, capes and other accessories to buy.

Cyril Ives and his partner set up the business two years ago, aiming particularly at the party market. "We put together a whole look. The hire fee includes everything - accessories, jewellery and false eyelashes, if necessary."

Stagestruck is getting a lot of work from people in the City, where theme parties are de rigueur. And top of the list? Seventies' nights, of course, closely followed by Grease, James Bond, Cowboys & Indians and Titanic. Already they are sourcing party wear for the Millennium: "We have created a lot of androgynous and futuristic costumes, and there's a lot of nostalgia for historical costumes."

Of course, costume hire is only worth it if the costume is a one-off ,or if, like those at Stagestruck, it includes the right accessories. Anyone with a little imagination can make their own. Or if it's a vintage dress you're after, buy rather than hire - you never know when it might prove useful or, more likely, back in fashion.

Angels & Bermans, 119 Shaftesbury Avenue, London WC2; Monday, Tuesday, Friday, 10-6; Wednesday and Thursday 12-8; enquiries 0171-836 5678. Arrive at least one hour before closing to allow time for fittings