Dublin is great - so much to see and do with lots of history. Small enough to walk everywhere (just!) but large enough to have plenty of sights. Lots of museums, churches and cracking bars. Airport is just north of the city with plenty of good buses.
If you wanted to stay in the UK Bath is beautiful with lots to see and do. The actual Roman Baths themselves are fascinating.
If you wanted to stay in the UK Bath is beautiful with lots to see and do. The actual Roman Baths themselves are fascinating.