I've walked around what used to be the "three Hs" - Heston, Hounslow Heath and Hanworth Air Park - They are all within a few miles of where I live. The last of those is still substantially as it was when it closed in the '40s.
Brooklands isn't that far away from me either - although technically it's not actually closed, but aircraft movements are very few and far between. The old Wisley aerodrome at Ockham common is another great place for a walk, which I do frequently - a bit of a drive to get there though. It's not exactly vanished, but it's been closed since 1972.
SD