As someone who lives very nearby, I was surprised to find this field messing around online on maps. It usually isn't that busy, but beware of the muggles & the many doggles that go with them. It's a lovely walk around, and I recommend you go around the heath, rather than just going for the cache.
It has started off ife with a pencil, but these have a tendency to dissapear, so you may need to BYOP.