I tried to get to Gorsey Bigbury the other week, but was stopped by a farm and very overgrown path. There is another henge at ST560500 which I have been to (no idea about the name), which looks to be of a similar size as Gorsey Bigbury. Whats left of the one at ST560500 looks like a classic although slightly small henge.
The priddy circles I don't really know though. They looked like henges to me, though the banks did a certain difference about them. IIRC they are low but not that spread out.