Um, Druid's Altar is (roughly) west of Grassington, quite a way. just the 'other side' of Threshfield, on the tops between Threshfield & Malham.
I've come across refs to the site you're talking about before, but never been able to suss it/devote enuff time to investigating.
It'd surprise me if it's Dumpit - wrong direction etc, but there IS a whole shitload of stuff near the 'circle' itself. Unfortunately the whole lot's swathed in heather & vegetation so it's difficult to spot what's what.
Fitz or Paulus might have some comments if they're around?
love
Moth