Hi Stingrayza
SW20 is very close to myself. (CR4) I walk to Wimbledon Common often and have flown at the common (of course taking off on a public footpath).
Mitcham Common is good. Morden Park ok. Richmond park over rated (IMHO). There is a few places in drone scene.
We have a meet up near-ish on the 6th August
Cheers
Brendan