In reply to limey:
Have a look at Afan. I've just got back from a weekend there with a couple of experienced friends, and one beginner(ish).
There's a campsite at
http://www.afanforestpark.co.uk/Default.aspx?page=6342
Decent showers, a good bike shop, bike hire and the centre cafe does a good breakfast and a decent evening meal, including a range of beer, wine etc and is open to 10:30pm.
We did the Skyline route which was pretty good, with a few boring sections although the final descent was excellent (but with technical bits) all of the route is rollable apart from a few drop-offs on the final descent, but by this time with a bit of coaching our beginner was fine with these.
Although its graded Red, the only section that really merited it was the final descent. It has a diversion on it at the moment, and is only 30Km. Some great views from the top across to Pen Y Fan.