And on mulling it over I could have sworn I'd read the stone was on the ridgeway itself (rather than further down). I'll look it up this evening if I remember.

Well blow me, it says "It's also where the term "Flibberdy Gibbard" cames from meaning one whom could not organise a p**s up in a brewery, Which Ironically was a favourite insult of my Great Grandmother! "
I was brought up on the term, though it was corrupted to "flippitty gibbet" and it meant an empty headed girl who flounced about in fancy clothes. Specifically, my sister.