I'm not an expert on Irish costume, but the English woodcuts that show the Irish "attrocities" in the 1640s don't show the Irish wearing distinct clothes from the English. Most specifically ECW Irish miniatures show them in tight fitting trews and fairly shapeless sack coats. So, I'd say those figures are probably too early for the ECW. See Warlord Games and Eureaka Miniatures for examples of ECW specific miniatures.
Also remember that, as always, Ireland was a good recruiting ground for mercenaries to serve in Europe and that there is an excellent chance that those men would have acquired fairly standard European style clothes (though how long those would have lasted back in Ireland is moot). I suppose a great deal depends on what exactly you want to portray.