It looks as complete as we're going to get it.
Had a quick look through the list, and it would appear the majority of these remaining stations are in Northern Ireland.
To my knowledge, Northern Ireland stations don't use the National/Network Rail codes system so it might be a bit hard to clear that list (The NI Railways page says they have 54 stations) and I can't seem to find any reference of any similar system existing for NI. There are a few station groups which, AFAIK, don't hold codes - they're certainly not on the National Rail published list. Same applies to the Tube stations in there, and the few proposed stations.
-- Lewis Cawte