I know quite a few Christians in the North and they always talk about going to southern Ireland for some meeting or another. I thought the regularity of this was odd presuming there must not be too many Protestant Churches in southern Ireland.
I did some digging and it looks like picture in the South with regard to non-mainstream Catholic Churches is not what one may expect.
Here is a bit of an idea for you. A cursory look reveals at least 60 Churches.
Jehovah Witness Kingdom Halls:
Church of Ireland:
Some of the Churches are old Church of Ireland chapels and stuff that have managed to hold onto some of their premises from the old days but the reality is a lot of these Churches are totally new.
A good example being Swords Elim, who on their website claim to be part of a network of 550 Churches in Ireland with 500,000 worshipers.