Now here's a good idea. AirBnB is a website which promotes people's spare rooms, holiday cottages or empty houses for tourists to use. Neat idea. The idea after the co-founders let blow up mattresses on their floor during a busy conference. It's even diversified into storage space, cars etc.
Look at this place in Notting Hill - $139/night for two people - bargain: http://www.airbnb.com/rooms/37094