I have a PAYG from Eircom.net for the last 4 years or so and find it pretty good - I am only there every 3 or 4 months for a couple of weeks at a time and have never had any problems with it being cut off / disabled. I can also pick up any mail sent to me via that account from here.
click here# for their flat rate service - €29.99 which is a little more than we pay here. No minimum contract.
UTV have one at €24.99 but I have never used them so cannot comment on how good they are: click here