There are loads of cairns up here, some are more cairnish than others, the ring cairn type one the big stoned kerb cairn, the grassy bump type and the stone rubble with a pit in type. But, the latter is not a cairn, there is one on the circumference of the stone circle, that's not a cairn, there is one by the Giants grave, that's not a cairn either. They are both in fact mortar pits dug by practicing soldiers waiting for D day in WW2. Perhaps a more poignant type of monument than most cairns, or perhaps not.
For directions to the general area, see the record for Mardon Down.
There are 4 cairns marked on the OS map. Two are apparently where the track kinks to the right half way between the stone circle and the cairn circle (SX767874). And two are supposed to be very close to the stone circle, one shown on the map as maybe 50 metres south of the stone circle, and one immediately north of the stone circle. Hmmm, well I didn't look for the northern two because I wanted to see the cairn circle and then go.
But I did find what I thought was a kerbed cairn just a few metres south of the stone circle. However that doesn't tally with the map. Curious.