Here's the aerial view:-
http://local.live.com/default.aspx?v=2& ... &alt=-1000
Found while searching for known WWII remains in the area, I haven't had the chance to wander round for a closer look, and the locals I know from nearby have no idea what it is either.
The north eastern section is clearly some sort of radio related installation with a number of aerial masts, a building and some other bases at regular intervals.
To the south east there are three circular areas, the two smaller ones are overgrown, and there appears to be a wall or similar running between them. The larger circle appears to be maintained clear of undergrowth, with some sort of radial pattern visible within it, and a further clear area on its southern perimeter.
Probably innocent, but would be nice to know what it is.