Ameuter, are all your clients targetting the Irish market? I would plant the irish based sites on a hosting reseller account provided by an Irish Host and all the rest on a cheaper foreign account (UK,US,Germany)
I'm not sure if that is financially viable for you to have two seperate reselling accounts, that's something you would have to look into yourself...
A friend has used hostdime for their normal hosting service and he found them very good. This is their reselling package -
http://www.hostdime.com/services/reseller/ - Lets say 3 of your clients are irish market based, then you could drop down to a more affordable Irish reselling package....