In reply to jezb1:
plas y brenin outdoor persuits at capel curig have their own bunkhouse on site ,(from memory ,it was called hebbog cottage.)i have stayed there several times .
it fits your bill exactly .centrally heated sleeps alot more than ten,2 showers large well stocked kitchen (which can double as a training room if needed.)facility for drying clothes ,decent bar,climbing wall etc and very reasonable rates.price is depending on numbers though.
worth a phonecall maybe.
gd luck