Thanks, David. That's a really useful site. But I can't see anything that fits the bill. It was literally within sight of the sea and none of those look so close, although IIRC it looked the most like Boskednan, I think there were more stones...
It'll come back to me! Anyway, it was an obscurer one and fairly hard to find. Compounded by the heavy fog that day. As we arrived, the fog lifted... just above and around the stones. We stayed there about 15 minutes. Then fog descended like someone dropping a veil. Husband said "I think they want us to leave." (Not usual for him to say stuff like that). And we left. It didn't feel hostile, in the sense that the fog lifted as we pulled up. No-one else was there. No-one else arrived whilst we were there. But it was very much a feeling of 'OK, you've seen what you came to see. Now leave!" at the end.
The circle I get to most now is Castlerigg, up near Keswick. And I always find that feels 'welcoming' but it has so many tourists it is hard to be alone there (Maybe I should go this winter). Went with a pagan friend and she said she couldn't feel anything there, whatsoever - because of the people being around. I have heard of other people going there and getting that 'hostile' feeling though.