Trywern sounds good.
When would we go up?
Accomodation? Prices?
Distance?

Times would be open for discusion, I would be game for an early oclock start sat. Camping most likely, usually about 7 quid a night.
Distance ... long, usually works out about 20 - 30 quid a head for fuel with a 4-1/2 to 5 hour drive. So your looking to leave about 5 in the morn for a decent days paddle.
Other options would be a day trip somewhere. Current forecast suggests we might get a fpre season visit to dartmoor in! Or a trip to cardiff?