Hi Mark,
Just saw your post Mark.
Only going on memory -
Dave in the Bierhaus found Zero Degrees Brewpub pretty good. Also look up Cardiff Camra page. I forget the name of one of the main pubs owned by Brains brewery but at the time that sounded like being worth a call too. Also a very big Wetherspoons pub (might tbe west county hotel or some name like that I think).
As I said unfortunately I did not get there. Maybe another time.
Enjoy!