During the Summer Solstice, We camped out on National Trust Land just by Stonehenge. We all had a great time with 20 or more tents pitched over a few days we left the place as we found it with no requirement of paperwork or consent from illusiary authorities.
The guy from the National Trus was really a nice guy and we all left the site on amicable terms.
Freedom is a possibilty, you just got to act on it. But always remember to be courteous.