The problem is not Ireland, the issue is if you are going to transit through the #$#%@
of Heathrow or other airport in England. The security is extremely ratty about the size of hand luggage.
I was flying by British Airways and according to their regulations it was OK to carry my set on board. I was carrying just a practice set at the time, but the case was a bit larger than usual. When I returned, it was fuller and ocupying more volume (with all the things that I bought and packed) and again, in the flight from Ireland it was OK, no prob.
I don’t know why the heck when I was going they allowed me to carry it, but when I was returning the
staff wouldn’t let me carry unless it fit into the minuscule tiny ridiculous standard grid that they have as a model template for the “appropriate” size.
I complained at the company desk, but they said according to their regulations it was OK, that it was a problem of the “airport internal regulations” 
With all this terrorist stuff going around, they are getting overly strict about hand luggage and you run the risk of having to dispatch it at the last moment, like I was obliged to do.
I think I read somewhere about a kind of international treaty that allows musicians to carry their instruments onboard, but I doubt that the staff would cede if someone showed up waving some kind of document at them or trying to explain the situation. I tried to explain and wanted to know why when I was going nobody told me anything and then suddenly this rigorous treatment when I was coming back. There were no buts nor further explanations, the guy simply pointed at the grid : -" Did you hear me? Does it fit it there?"; that is, if it doesn’t fit in the damn grid, NO WAY. I got really mad. 
So, what to do? You can get everything confirmed and reconfirmed, the company told me was OK, I checked at the airport when I was leaving and then this surprise when returning?! So, I would take with a grain of salt if everybody says that it’s everything OK. Double check and expect everything, being ready for a plan B 