For mine we went to Baskerville Hall in Hay on Wye and then did activities in the surrounding area. You’ve got Brecon Beacons and the River Wye right on the doorstep.
The hall has dirt cheap dorm type rooms (rooms with bunk beds sleeping 15+ people), the breakfast was ok, nothing fancy, just a load of fried food, coffee, juices etc. The grounds are large, so you can play football in the evening while drinking beer from the bar before you go into Hay for more drinks.
If you’d prefer somewhere with busy pubs and a great nightlife then Hay on Wye is probably not for you. But Hereford isn’t that far away, it’s a little more lively and has a strip club I’m told. One of the guys on my stag found it on the internet, and was desperate to go as he decided he was entitled to see boobs on a stag do, but noone else fancied it.