Simon,

This question arose on another site and I took a trip out there, nothing really to be seen at ground level, however we did note that these sites had fencing round them and there were signs saying about shooting parties so maybe pheasant enclosures?

Also the oval ones:

http://www.flashearth.com/?lat=52.913279&lon=-0.51982&z=16.6&r=0&src=ggl

Notice the strips of land near them too?

Maybe another trip out there is on the cards, also they’re not HAA sites, however this is:

http://www.flashearth.com/?lat=52.913279&lon=-0.51982&z=16.6&r=0&src=ggl

The HAA link:

http://forum.keypublishing.co.uk/showthread.php?p=1221557#post1221557