Okay, a trip down to Connemara gave me the opportunity to bag a few lighthouses, but with my wife accompanying me, I could not perhaps devote enough time to tracking down some of the more distant ones. A couple of the photos are quite disappointing but the prospect of another journey down to rectify this softens the blow somewhat.
This is the Cashla Bay Light, located at Latitude 53°15.834' North Longitude 009°33.982' West according to the CIL. The lighthouse directory does not list it as a lighthouse, though most road atlases do.
To find it, come into Rossaveel and continue down around the harbour, past the Aran Islands ferry parking, until a wrought iron gate marks the end of the road. There is a pedestrian gate through to the other side but as the light points out to sea, it is difficult to get around to the other side of it. Probably the best view would be from the ferry.