Certainly at Boscawen-Un, the stone is actually at the layby on the A30, nowhere near the circle itself. Similarly at the Merry Maidens (Lamorna), the stone is outside the field which contains the stones - again, in the layby on the B3315. I don't have a photo unfortunately, but the text includes the info that was on the original paper notices, and includes a phone number to report any problems.

The guys in Cornwall have put a lot of thought, time and effort into this and are to be applauded in my view.