Before buying a new home, you hire a solicitor to ensure no-one's planning to build a motorway at the bottom of its garden, and a surveyor to check for dry-rot. But when it comes to uncovering factors that could cause equal upset - neighbours regularly into all-night parties, for example, or roving bands of crack dealers - you're usually on your own. Assessing an area's quality of life requires lots of legwork, late nights, and knocking on strangers' doors.

Or you could employ a team of professionals to do it for you.

An increasing number of people are now turning to private investigation agencies to thoroughly vet their intended location and present a picture of what it's actually like to live there. Answer Investigations, based in Godalming, Surrey, was one of the first to offer such a service. Director, Nigel Parsons, explains. "An area that, during the course of a 20 minute visit in the company of an estate agent looks ideal, can in fact turn out to be an absolute nightmare. Maybe the road is used as a rat-run each morning. There could be noise from local pubs and clubs. Or, more likely, from neighbours. Unfortunately, annoying the next-door neighbour seems to be fast becoming the UK's national sport."

Who exactly uses such a service? Many clients are referred by multinationals looking to relocate their staff to the UK. Because they themselves have little, if any, local knowledge, the agencies' expertise can be invaluable. Liz, for example, who moved to England from Boston six months ago, was saved from making what could have been an expensive mistake.

"The house was described by the estate agents as being in a quiet residential area. It turned out to be in the heart of Brixton. Now here, of course, Brixton has something of a reputation. But not where I come from."

Even apparently idyllic locations can have their drawbacks. "I bought a flat in very up-market area," says William. "My first Friday night there, there was shouting, and banging of doors. Suddenly, there was a terrific crash. I looked out to see that a television had been thrown from the window. Then everything went quiet. I assumed it was a one-off domestic dispute. But the following Friday, it happened all over again at almost exactly the same time. When I talked to the neighbours, it turned out this was a weekly event. They could almost set their watches by it. The next time I moved, I hired an agency to check everything thoroughly. I didn't want to make the same mistake again."

Such agencies tend not to advertise. However, your solicitor will usually be able to put you on to a reputable one. Thereafter, costs vary according to the sort of service required. Typically, you'll pay around £300 for what's termed a "neighbourhood report." A large part of this - indeed, often the most fruitful - is compiled from interviewing the locals. But how do the agencies know whom to interview in the first place? And how do they get them to talk?

"There's a lot to be said for wearing a suit and tie and being friendly and polite," says Parsons. "I'll tell them I'm thinking of moving into the area and am looking around. Then it's very easy to get people to open up. The local moaner and the local gossip are always the best. If there are problems, or if someone has a reputation, he or she will soon tell you."

Checking out the amenities is also useful. The pub, for instance, tends to act as the barometer of a neighbourhood. If drinking there is a survivable experience, it usually follows that the area itself is fairly respectable. But a lot of the agencies' work consists simply of sitting in a parked car late on a Friday and a Saturday night (when any problems are most likely to present themselves), watching and listening.

Aside from this "fieldwork", the investigation agencies carry out background checks. The first stop is usually the local police station, where an area's crime and burglary statistics are kept. Then there are occupancy records, courtesy of the local authority. If these show that people tend to move out after no more than six months, it hints at problems. A lot of useful information, too, can be gleaned from a thorough examination of newspapers, particularly their Letters to the Editor pages, where most local gripes are aired.

At the end of the day, however, it isn't the agencies' job to give a verdict, merely an accurate report. Who is to say what suits you? To many, having, say, reggae music blaring day and night might be considered a drawback. However, if you're a committed Bob Marley fan, it could be Paradise.

"We won't draw conclusions," says Parsons. "We simply write a report. What the client does with the information is up to him. A house is the biggest purchase of your life. You can't afford to make mistakes. If the reality doesn't match up to your expectations, you'll be bitterly disappointed. Our job is to ensure you're not."

Answers Investigation: 01737 223 278