I think I raced at all three, depending on the answers to the questions below
Oaks Park Ramblers - was that the grass track that was on the entrance to a golf course?
Was Thornton Heath Off Roaders by the crematorium? A worn grass permanent track if I remember.
Surbiton Off Roaders was by a football club, a go-kart track and a caravan park, yes or no? Multi surface from what I recall. Parking/pitting wasn't exactly track side...