There's one on the edged of town called 'The Last in First out', i.e. from Wales to England. It's like a timewarp back to the 50's featuring Ales you'll never heard of, and probably won't again.
It usually looks closed but isn't.
There's plenty of others as well though in town - all nice.
If you're further afield , The Skirrid's nice, The Star in Talybont ( bring sleeping bag as they let you sleep it off on the floor )