Hi there
I second the proposal for Denham and not being biased I would try The Pilot Centre.
(
www.egld.com/tpcwelc.htm) Contains info for Denham airfield and The Pilot Centre.
The Pilot Centre is run by Chris Leach and the tel no. is 01895 833838
As stated before you can either take a train from Marleybone to Denham station or you can go on the Metropolitan or Picadilly line to Uxbridge Station. You can then either take the 331 bus and then a 15 min walk or take a cab for £8.50.