Sorry, but my colleague was not that helpful. They have been to the same places by what he said, Woolacombe being the first one he suggested, so I have tried to have think myself. Do you try and stay in a place with lots of things to do, like on the coast, or is it just to spend time out in the open air?
I have done very little en mass camping. Inland, I have took part in a long charity walk along the ridgeway, where there were three base camps. The first one was at a farm in Watlington, Oxfordshire that would have enough room for you plus had water and toilet facilities. The final camp was at a farm near Barbury Castle, and there was a halfway one between the two, would need to look the name up of that one. All three places do not have a lot 'to do' around though, except for walks, views etc.