An interesting thread, Colin.
Very little British stock can do anything other than the very vaguest resemblance to Irish stock. Some English LMS stuff can resemble some NCC stock, and the old Triang GWR brake third with the bowed-in ends resembles a pair of Waterford, Limerick & Western Railway brake thirds built in 1898 and withdrawn in 1955 by CIE. (One compartment too many, though).
Thats about it. Worsley Works do a great range of Irish stuff, but as seen elsewhere on this site, they take a bit of skill and experience.