From Heathrow you can take the London underground using the Piccadilly Line, which will take you right into the West End, via Knightsbridge, Green Park, Piccadilly and Leicester Square. The cheapest and quickest way to reach town is by the Express train which takes 30 minutes. Once at Victoria Station, there are several buses as well as a taxi rank, and Oxford Street is about 10 minutes' drive away. 680500 Stansted is a 40-minute train journey from London's Liverpool Street station and trains run every half hour. It boasts an unbelievable check-in time of 10 minutes and current flight destinations are Brussels, Berlin, Antwerp, Amsterdam, Frankfurt, Rotterdam and Zurich.
Buses are very frequent throughout the city and are a cheap way to travel.
The tube is cheap and accessible, and when it is not held up by faults on the line, it is faster than anything with an engine on the road. It stops running at around midnight and resumes at 6.00.