Where's hot, and not, to live

This colour-coded map of London shows how much each room in your home could be worth, to the final square foot.

The map, drawn up by agents Hamptons International, shows the most expensive floorspace is in the traditional haunts of City workers looking to spend their bonuses.

The highest prices are in the SW7 postcode - South Kensington - where homes are being sold at £1,235 per square foot. That means a modest 12ft by 10ft bedroom could cost almost £150,000.

The agents surveyed 55 of London's postcodes, the cheapest of which was SE19, which includes Crystal Palace, Norwood and Upper Norwood. There, homes sell at £350 per square foot - so the same room would cost £42,000.

The average price was £798 per square foot. Rob Bruce, Hamptons' research manager, said: "Despite predictions on reduced City bonus payouts, we have seen a stream of investors spending or looking to spend in the prime London markets, like Kensington, St John's Wood and Richmond.

"Some of the money is also going into the areas in which City employees live, such as the South Bank."

Mr Bruce continued: "On the outskirts of prime central London, one of the strongest performers was South Lambeth/Nine Elms (SW8), which continues to be the most expensive central London location south of the Thames.

"Even in the cheapest area, Crystal Palace (SE19), the price of £350 per square foot is the same as the most expensive new properties in places like Glasgow." Meanwhile, the number of new houses being built in London has reduced dramatically over the last decade, as developers build flats instead, Government figures show.

Only one in seven homes built in London last year was a house. In 1997, the figure was 50 per cent.

Stephen Ludlow, of estate agency Ludlow Thompson, said: "These statistics are worrying as the demand for houses keeps growing. We are heading for a situation where many families aren't going to be able to rent or buy the kind of home that meets their needs. The last 30 years have seen a need for smaller properties for smaller households, but the pendulum has swung too far."

Nationally, 47 per cent of new properties are houses.

HEAT MAP SHOWING THE HOTTEST PARTS OF THE PROPERTY MARKET