Thanks so much for all the info! Very helpful stuff.

Visiting Cardiff filming locations is definitely on the agenda, along with the Doctor Who Exhibition.

I may well hit you up later for more Ireland details. That sounds very doable. Train rides through beautiful scenery are always a plus.

Youth hostels are the place to be. I'm a sound enough sleeper to deal with the shared dorms, and I really like how hostels make it much easier to meet people than traditional hotels.