My advice JKT is to get the mortage on the portugese property - not on the Irish property. With regards to the tax relief I know in spain you can offset the income tax from renting against your mortgage if taken out in Spain. I don't know much about the portguese market but really you need to ask some questions on a forum geared for portugese property. There are plenty of forums for the spanish market. Inform yourself well about local taxes, what taxes you pay when purchasing a property, do you pay a yearly tax whether you rent out the property or not. What costs are incurred for maintenance if it is part of a development, what costs do you incurr if you wish to sell.
Angela59