Ta for the info on that wysefool, the picture is fine as it is - no need for a higher resolution scan :-)
Looking at a plan of both sites, Notgrove is very closely related to Nympsfield except that it has a couple of extra chambers.
Also I’m not sure the author got his directions right in the text – if that drystone wall to the bottom left is part of the forecourt then the picture is looking from the east.

Cheers-
Chris