I was looking at that book, Stones of Adoration http://www.amazon.com/Stones-Adoration-Sacred-Megaliths-Ireland/dp/1905172362 last night, i got it out from the library.
I dont have it in front of me but I think I remember seeing a section about Glencolmkill in it.
Might be worth a look.
She has your folklore about the bullaun stone in Ardmore beach as well. Expands on it by saying that there was a rumour that the bullaun stone was in a private garden until the 1940s.