The Flower class corvettes were based on a pre-war fishing boat design from Middlesbrough. This leads nicely to another angle to consider - the trawlers. From 1939 several hundred fishing boats were commandeered by the Royal Navy for light duties, along with their crews. They certainly proved their worth.
These included mine sweeping, mine laying, anti-submarine patrols, convoy escort, air defence, boom defence (harbour guard), Dunkirk/Narvik/Tobruk evacuations, delivering spies and special forces ashore and general training.
There is no reason for Ireland to not do the same around her harbours. This could be the start of the Irish Naval Reserve.