Regarding the Markshall sites are visible on Google earth, select 11/9/2006 photo. :-)
Site 1) 52° 35' 39.21", +1° 17' 50.74" diameter ~40 meters
Site 2) 52°35'35.77"N 1°17'50.32"E diameter ~28 meters
A third can be seen on the 31/12/1999 photo.
These look like round barrows that have been progressively ploughed out from 1999.
Something is not right. This message is just to keep things from messing up down the road