My latest issue of the Cornwall Archeological Societys newsletter has a nice feature on the work of the Cornish Ancient Sites Protection Network. cornishancientsites.com/index.html
They have a number of site clearence days coming up througout the year (see website) which I might try to make and are also working to erect boulders at the entrances to sites with engraved phone numbers on them to ring to report vandalism or damage and also info about respecting sites.
Full marks to them!