YOU WANT TO SELL. You need to sell. You can't sell. So what do you do in this frankly flaccid market if your house is sticking like an old plaster and the owners of your dream home are making impatient noises at the other end of the chain? Well, you could think of calling in an interior designer.

Many people think of interior designers as well-groomed women with glossy hair and even shinier views, who will demand that you spend scary sums of money and will boss you around while you're doing so. But interior designers - and their clientele - have undergone a major image shift in recent years.

"Ten or 15 years ago most people wouldn't have dreamt of using an interior designer; they would have just said 'I'll do it myself," says Mary Leslie, vice-chairman of the British Interior Design Association, and herself a successful interior designer who has worked for both the Duke and Duchess of York at Sunninghill Park and for a wide range of private clients from as far afield as Sussex and Oman. "Nowadays, however, there's so much choice in fabrics and furnishings, in kitchens and bathrooms, people have begun to realise that an interior designer can save them both time and money."

Employing an interior designer may no longer be the preserve of the very wealthy, but it's never going to be as cheap as going to Ikea and wielding the paintbrush yourself, like using a top barrister or a clever accountant, however, it can end up saving you thousands of pounds, and can certainly aid the under-confident or time-pressed to bring their house to a picky market in a buyer-friendly condition.

"It is very difficult to say to someone who's thinking of selling that they should redecorate," says Linda Beaney, co-owner of the Chelsea estate agents Beaney Pearce. "But sometimes you have to explain to them that, in a market where there's a lot of choice, their house will simply not make it on to a buyer's shortlist if all the key rooms - the drawing room, the master bedroom, the bathrooms and the kitchen - are not well presented. Not everyone knows how to do this themselves."

Though it's unlikely that you will want to call in an interior designer to do a complete make-over when you're selling, you may wish to take advantage of a designer's hourly rate - ranging from £50 to several hundred pounds - to give advice about soft furnishings and paint colours or to supply working drawings to redo a dated kitchen or a tired bathroom.

On larger projects most interior designers prefer to work either for a flat fee or for a percentage. "In the past designers used to make their money from the mark-up on the goods they supplied," explains Mary Leslie. "Now they are increasingly separating out their professional expertise. They will itemise their design fee, and then supply goods at a low mark-up, so that if you wish to buy furnishings or fabrics from someone else, they are perfectly to do so."

So how do you go about finding an interior designer? Personal recommendation is clearly one of the most reliable methods, and good estate agents can often suggest someone who they've worked with in the past. If not, the best route is through the trade associations - such as the British Interior Design Association - which vet their members and increasingly put them through various qualifying tests and interviews as well.

Many interior designers now have websites, where you can view examples of their work, and it is general practice to set up an initial meeting for the designer to show his or her portfolio and see whether you get on.

"This usually comes out quite quickly in conversation," says Mary Leslie, who has more than 20 years experience and, before setting up on her own seven years ago, ran Nina Campbell's decorating department. "There will be a definite empathy, you will be having a laugh and relaxing into it." After that, you will almost certainly want to take up references before making a final commitment, and will want to see a detailed estimate of everything you have discussed in your initial meeting.

"You should liaise with your agent, too," recommends Linda Beaney. "Some designers have too individual a style to appeal to the market in general, which is fine if you're going to live there but not if you are trying to sell. The agent can also let you know if you'll be spending more money than you'll recoup."

One of the greatest benefits that an interior designer can bring to remodelling a house is knowing how to rearrange the space to get the most value out of what is available.

Carol Bennett, director of Designed Interiors, is an interior designer with a long history in the property business and has worked for estate agents, developers and private clients in the buy-to-let market.

"Everything nowadays is sold on square footage, and it's part of my job to make sure every square foot works to its best advantage. I might suggest how a client can knock a number of small basement rooms together to create the large kitchen-diner that most London purchasers now look for, or how they might create that essential downstairs cloakroom, or rework an underused spare bedroom to make another en-suite bathroom."

Carol even offers the relatively simple service of rearranging existing furniture to ensure that the living space is harmonious and uncluttered, and can also advise on window treatments that might help to hide unsightly views or make a room look lighter and larger.

Most interior designers can also provide builders they know and trust. "I always use the same team," says Carol Bennett. "We have an ongoing relationship, so they know they have to do a good job, and they also understand how to work around each other, so that a job can be carried out much more quickly."

Speed, of course, is everything if you are attempting to prepare your house to catch a seasonal market, and Carol Bennett allows just six to eight weeks for a "tart up". "For a small terraced house, it takes about three months from first meeting to completion - depending on how long the client needs to make decisions."

Because of her commercial background, Carol Bennett is particularly aware of the need to get things done yesterday. "Only 30 per cent of interior design is actually about design, the rest is about organisation, schedules, budgets and chasing suppliers. You can't leave anything to chance. My job is to take the stress out of it for the client.