Greenham common is near Newbury, it's been the test site for my little Tamiya buggy
At the end near the drainage pools, near Thornford Park, there's loads of bumps and troughs - kinda like a moonscape. A mix of uber short grass (thanks to the horses & cows) and gravel, with a few little short hawthorn bushes that make things interesting. Plenty of flat bits to go fast on, other bits that are steep enough to be challenging ... I'm looking forward to summer when the pools are emptier so there will be some more extreme surfaces to drive on!
It's only really suitable for electric vehicles, because of the aforementioned cows & horses (plus many dogs, kids on bikes etc), but thats about it. Oh, and the bit around the bunkers where they filmed bits of Star Wars VII are pretty cool to look at, too