If your interest is in British outline, USA or continental, great for N, but as regards Irish stock, my only observation is that effectively there is no Irish Rail nor CIE RTR stock available in N gauge, so you would have to convert, kit bash, build your own stock using BR RTR donors possibly with the aid of some of the 3D bodies available (shapeways) that might fit on Graham Farish loco chassis. Not inexpensive and not an easy path.