I'm not sure how well suited it would be to beginners.
They hold lots of downhill races there (one happened today I think), and they've built some pretty tough courses.
That said, I've heard that they've been doing a lot of work there lately, and are even putting in a road circuit, so maybe they're broadening its appeal.
Here's their site:
http://www.porc-online.co.uk/
Another place to consider with marked off-road trails, and likely to be much more family friendly, is Bedgebury. Although it is a fair but further, being over near Bewl Reservoir.
Here's the Bedgebury site:
http://www.forestry.gov.uk/website/recr ... mandForest