Thank you, Gadget. Yes, that must be it. I love maps too, so it's good to see another source to search. It was certainly worth asking. It looks as if Penfeidr was just perhaps a house or farm but now I know which part of the parish it was in. Ironically we drove back from holiday in Pembrokeshire last week, probably just a few miles away from the spot. Many thanks from South Wales!
Brownie.