I should have been clearer in my first post - I don't think it is a stone circle.

It's in a fairly prominent position not far from the main path up the hill, so if it was something of "antiquarian interest" I'm sure someone else would've spotted it before.

Also, as you say, it's in an odd position for a monument of some kind, almost falling off the side of the hill.

But it does look circular in form, probably clearer in reality than from the photos, and I was just looking for opinions as to whether people thought it was just a fortuitous natural arrangement, and if anyone had come across anything similar.