Directions :
From Heathrow International Airport: Take the Piccadilly line to Earls Court and then on to the District Line getting off at Bayswater.

From Gatwick Airport: Take the Gatwick Express to Victoria and then change to the Underground taking the Circle Line to Bayswater.

From Stansted Airport: 
Take the Train to Liverpool Street and then change to the Underground taking the Circle line to Bayswater. 

More Information about the:
Heathrow Express
Gatwick Express

Stansted Express
London Underground