I was out in Aberystwysth a few weeks ago and there were some trails in that area, east of the town I think.
Can't remember what it's called, but I thought it was good, contrasting with most of the mtn biking area I've been to( Afon Argoed, Cwm Carn, Coed Y Brennin, etc ) as there was alot not in trees, so it seemed more open.
Colin