Yucky-dah boyo! I'm jealous of your locale.
When lived just outside London, every year me and the boys would ride to the Brecons and then up through Snowdonia, to speed a couple of days racing.... erm, I mean, riding around the fabulous roads you have up there.
I've done the off-road course with Dakar rider Simon Pavey in Wales and loved it - highly recommended. Fit some Conti knobblies and try to get a discount for riding the course on your own bike! ;-D
Anyway JOL, enjoy and let us know how you get on. Especially if you get the chance to ride Newtown to Builth Wells - or Assen in the Sky as I like to call it - best biking road in Britain IMHO.