You can go to any Notary in Ireland who witnesses your signature but you must have an original of the document possibly with official translation to be notarised. Just bring your passport for ID. Problem is you will also then have to go to Foreign Affairs to get the doc. "apostile" stamp. Combined fees possibly in the region of €100. So make yr appointment in Dublin with the Notary but allow time to get over to St.Stephens Green with the notarised doc. before Dept. Foreign Affairs office closes , might be 4pm.?
However in my experience the Spanish Notary fees are officially regulated and not expensive. At this time of year the air fares are reasonable considering it is important business and opportunity to take a day or two for leisure. Why not just go over to Spain or tell Solbank to wait until your next planned visit.
The Notary in Spain has a role which extends beyond that normally handled by the Notary Public in Ireland - the Spanish Notary examines the title and also registers the property transaction in the Spanish equivalent of the Land Registry. The lending bank want this done to protect their interest. I see no option but to meet the requirements of the lending bank.
Have very reliable and honest Spanish financial representative in Tenerife, Canary Islands. Sister in partnership who is a solicitor. Should anybody want the address I will be happy to give it.
He has been representing us for 9 years. He pays our taxes and does anything necessary for a very small fee. He recomended the Notary for our needs. He also facilitated us with the purchase. Browtal