I HATE car hire companies with a passion. After I got scammed by one of the big "reputable" ones for damage I didn't do, I swore I'd never use any of them again. Been using economycarrentals.com ever since. Sorry, though, only used them abroad, never in Ireland, I have no idea if they do business here. Basically they arrange car through small local companies you deal with. I am not vouching for them -- just saying I got a personal service and have not been scammed yet. My view is that if I am in danger of being scammed anyway I might as well get it as cheap as I can (and they have been very cheap).
I have no connection whatsoever with them, and as I said, am not even particularly recommending them ... just recommending against the overpriced more respectable cowboys.