The best advice on driving in London is this: don’t. London’s streets are a winding mass of chaos, made worse by one-way roads. Parking is also restrictive and expensive, and traffic is tediously slow at most times of the day; during rush hours–from 8 am to 9:30 am and 4:30 pm to 6:30 pm–it often grinds to a standstill, particularly on Friday, when everyone wants to leave town. Avoid city-center shopping areas, including the roads feeding Oxford Street, Kensington, and Knightsbridge. There’s virtually no reason to rent a car if you are just staying in London; the city and its suburbs are widely covered by public transportation.
From the Forums: London itinerary help needed plus a question about the Tube