There are about 5000 Piperstowns in Ireland, but you are right, the grid refs are very close.

I was (once again) looking for the stone circle when I found the stone (and possible associated stone row). I don't believe the stone circle ever existed and Burl got his info mixed up. There is a stone circle at Glassamucky Brakes just 400m or so away, which I think is the one that Burl has down at Piperstown. This is why I never added the Piperstown stone circle to TMA.

Irish sites are known primarily by the townland they are in and I am not even sure that the standing stone mentioned above is in the Piperstown townland. These days townland borders are pretty hard to work out without the original 6 inch maps - the new OS maps don't list them all and often have them in totally the wrong place.

Around this standing stone there were some excavations and hut circles were found as well as the alledged stone circle. This was revealed after a fire in the peat and was spotted from an aircraft. I haven't seen the excavation report so I am not 100% sure about the circle/stone mix up theory.

Setting Irish Grid refs is as easy as UK ones - e.g. S123253 or whatever.