Going back a few pictures, the only outstanding one for identification is this one:
Photo: N L Cadge, collection of John HinsonPoring over the Signalling Atlas & Signal Box Directory, I find the following listed as Railway Signal Company architecture, frameless, and used as a shed:
Cappoquin
Carrowduff
Killough
I'm hoping it may be one of these - can any be eliminated? Search engines have found me nothing on the web (although I am not renowned for finding things there) and Google Earth has left me with nothing - not knowing the railway geography well I am stumped when GE dumps me in the middle of a field with no apparent sign of a railway trackbed and tells me "this is the place".
John