Hey Patrick
Your normal membership minutes will not work when in Spain. They only work when in Ireland.
Cost wise you have a couple of options.
You can buy any of the EU roaming add ons.
EU Roaming VOICE - €3.50
Ten minutes of outbound calls within the EU.
Unlimited inbound calls within the EU.
Free to receive calls.
This will last for one calendar month.
EU Roaming text - €2
Twenty outbound texts within the EU.
Unlimited inbound texts within the EU.
This will last for one calendar month.
Or if you will only be using your phone in emergencies then just top up with some credit. You will then be charged for each call you make or receive and each text you send. See the costs here http://www.48months.ie/membership-plans/going-abroad under the "Standard EU roaming charges" section.
I hope this helps ~ Damian from 48
