It's my guess that 99% of people that climb on standing stones don't realise they shouldn't - which puts the blame squarely on the guardians. Yes there are sometimes notices saying don't but they don't say it clearly enough so that no-one can miss them. The French on the other hand -----
Yes I think there's a certain amount of truth in that Nigel. Kidz taken with parents who are there just for a day out but have no real interest have no reason to question anything so it becomes a playground...did it myself over and over as a kid. It is really down to the guardians as you say to provide wardens on the larger sites along with sign boards with decent and obvious notices on the 'lesser' ones as a minimum.