Hey guys, just found this thread while trying to find a decent bash spot in Kent. You'd think it being the Garden of England we'd be spoilt for choice!
Couple of places you might also want to consider that me and some of the Kent guys from TamiyaClub go to are The Warren in Ashford (great for crawlers, and the car park is pretty good for buggies if it's not too crowded), Pennenden Heath in Maidstone (just down from the recycling bit) and also the Pennenden park and ride on a Sunday when it's closed is really good too. Mainly gravel and bit of tarmac.
Had a bit of a scope out this morning of some of the other places you've suggested too, although I didn't see the post about Mote Park till I got back.
I'm 40, live just outside Canterbury, and I mainly run 1/10 electric cars (bunch of Tamiyas, 4x4 Slash, and a couple of Axial crawlers.)