In reply to Paul Hy:
Between the Count House and Morvah is a field (on a bend) which advertises camping places. Pretty basic, standpipe and portaloos, and as I recall only a couple of quid per tent. You'll not find it advertised anywhere, it's one of those turn up and pay later things that farmers enjoy using their spare fields for. It's been open for many consecutive years, so no reason to think it won't be this summer.
Leave the Count House, drive to Morvah, it's on the left on a right hand bend just before Morvah.