Is there another castle in Brecon? Seeems relevant if you want to go there before you go there as it were.
Details of the venue are useful, people use satnavs don't ya know. Without a contact telephone number of an organiser you could try the venue.

As I always say if going any distance - ring before you go, to check. If the organiser is not a folkie he may not understand the needs of attendees - not many folk organisers do - I can tell you.

Isn't Brecon a fair trek from BC? And not exactly en route to Devon.