There is a bus, 303 (indicated on the bus stop in front of the Colindale station), that stops at RAF Hendon.
There is a variety of aircraft.....depends on your interest.
I have, in the last two visits, been attending the archive. An excellant service with very interesting information. It is my favorite but I did, on the last visit, take many digital images of the BE2a in the Graham White factory and the Tempest.