We stayed in Trewellard, just by St Just (sic) a couple of years ago, in a cheap and cheerful campsite with free everything run by a strange lady and her probably now deceased Dad.
It was fantastic. Quiet, dark (stars x 10000000000000) beautiful, and an excellent base for tip of cornwall sites. We visited men an tol and several others.

Here's the multimap ref...

http://www.multimap.com/map/browse.cgi?X=137500&Y=35000&width=700&height=400&client=public&gride=&gridn=&keepicon=false&coordsys=gb&addr1=&addr2=&addr3=&pc=&advanced=&scale=50000&out.x=8&out.y=8