As Ocifant so kindly put me forward...
Not sure about the circle NE of the Pipers...not something I have come across. As Sanctuary says the Craddock Circle is NW..but you would be a long way of course to find it.
I think I know the two stones at Chysaucester you are talking about...are they the door jambs to House 7?
As for the stone row...like all the other stone rows on Bodmin Moor we have no idea what they were erected for...sorry!
All the best, glad you enjoyed your trip to Cornwall again.
Mr H