I would be inclined to agree with you in general there ExXB. Although I have asked an airline rep twice now and they have confirmed both times that even with separate tickets, the bags will be tagged through.
I'll wait for an answer from Irish customs about collecting at the first point of entry before I commit of course. Not much point going through the hassle of through-checking if I need to pick up and drop of bags anyway.
Many thanks for your advice again everyone.