To answer myself, the news report was here http://www.wiltshiretimes.co.uk/mostpopular.var.1751615.mostviewed.fred_flintstone_in_court.php
and so far as I'm aware the only law protecting a scheduled monument is the '79 Act and that prohibits damaging one not climbing on one. Its not illegal to climb on Silbury for instance.

If as a result they get away with it, no damage having been established, it may send an unfortunate message out.