Yes and all those red letter boxes would just have to be for votive offerings if a latter day Francis Pryor was one of your future archaeologists.<

:-)

>...to heft all those great big stones around to make a stock proof fence is just plain daft - and they weren't daft.<

Well, hang on a mo Peter. Take a circle like Castlerigg; once you've got your basic (stone) supports up it would be dead easy to maintain a fence between each stone (for a corral I mean). Thinking in reverse, how else would you construct a safe, solid and permanent corral other than with stone posts with a fence between each stone?

As you say, "...they weren't daft." but the solution is not dissimilar to modern grooved concrete posts that you slip wooden panels into (and replace when needed). I suspect that these places were not just corrals but semi-secure places for both human and livestock habitation.