I actually don't agree with the idea that "... this is about Avebury and the people who live there..." Avebury is a World Heritage Site and as such the 'world' has as much right to access and enjoy the place as the villagers do to live there (how you reconcile those two needs is a tough one though).

The question of trees in the circle is an interesting one - I don't think we should just assume the circle was ever conceived as being 'treeless'.