Having delved into the Catacombs, and perused 1950s working timetables for clues about signalling, I found out a little more.
Westport Quay and Cahirciveen - Valentia were operated then (and for many, many years earlier) as "one engine in steam", thus allowing little in the way of catch points, no ground signals and just one home starter, and home approach signal. This will make life MUCH simpler!
Valentia had had a signal cabing, but ended up with a ground frame; so did Westport Quay. The lever frame at Valentia both in signal cabin and GF days, had but five levers; three for points and two for signals. This would have meant one signal each for home approach and home departure. This, therefore is what i'll have, as my plan is to recreate the sort of small terminus which would have one mixed and one goods a day, coming to life big time whenever it was beet season, GAA All-Ireland day, or Knock specials.
This type of system was probably reproduced in other places in latter days; I know that Ardee cabin (which i was in one time) wasn't exactly packed with levers, and Castleisland could possibly have been similar.