Affiliate networks cost a lot of money to run properly and you need to have a certain number of publishers AND advertisers.
The Irish market is tiny
Spending money online does not equate with advertising and advertising does not equate with affiliate marketing ..
There are quite a few companies offering advertising management ie. they'll sell the inventory for several of the big publishers, most of the bigger affiliate networks either have an Irish office or have some focus on the Irish market. I know that there's one or two companies that are doing some things, but I'd suspect that the market is very small.
Along with the points BK has already made (especially in relation to economy of scale which is a major factor), it's worth remembering how much of the "Irish spend online" is going abroad. I don't have the figures off the top of my head (I've a vague memory of the report I'm thinking of coming from Google a number of months ago, if anyone remembers it), but due to the relatively poor ecommerce offerings of Irish sites the majority of that online spend goes to the UK or further afield. Things are improving here, but we've still got a lot of catching up to do.