We cannot yet target Ireland as a geographic region in the new Yahoo interface. This will be implemented by middle of September. I will keep you up to date once this is available.
It is possible to create a campaign for Ireland in an already existing account. Duplicate keywords are allowed as long as they target a different region.

Targeting Ireland as a geographic location has not yet been implemented, this will take longer according to Yahoo and I will keep inquiring to update you.

Yahoo has confirmed that the UK account geo targeting now works. You can create an account and only target Ireland.