I've just checked a detailed map and the area just to the east of your ref. point is named as Rodborough Common. I don't know the area very well - I live in Birmingham - and always regarded the common as being further north, which it is. Now, I can see that there's been a lot of building upon the common which has split it up. Thanks for the info.

I read that the vegetation had been removed from the Hore Stone by it's finders. With the growth upon it, it had appeared to be a tree stump.

baz