White Waltham.
London Paddington to Maidenhead by train will take you 32 minutes.
Maidenhead Train Station to White Waltham Airfield by bus (either the 7A or 7B) will take you 15 minutes, one bus departs every 15 minutes. The drivers usually drop you outside the front entrance of the airfield if you ask them. Two minutes later you'll be in the club house of West London Aero Club.