Thanks all for your comments and suggestions. I am visiting the area for a couple of nights and thought I would make the most of having the ability to get out on the trails, rather than just going back to the hotel and putting on The Wire on my laptop...
I have ridden from both trail centres a couple of times, but not for a while now (have a kid these days). I am actually going to be based in the Swansea area so will be heading back from the West to East, hence my thinking it would be easier just to head up into the valley rather then get back onto the M4 heading back towards the East.
I have ridden The Wall as an after work shortish blast before (in the pouring rain I seem to remember), but have not done any of the local rides. Shortish to me would be sub 2 hours, so that I am not too pooped, yet feel like I have been out for a ride.
David Jey, will email as any routes would be of interest.