There isn't a junior section to the club, but I think you're spot on about the best ways to encourage him. There are downhill races and uplift days (both quite chilled, so don't be put off)which are fairly within reach of Bristol. There are races at Cheddar, Churchill and the Dragon series in south wales. Doing events like these is where he'll probably meet riding buddies.

Thanks Rob - will keep an eye out for daytes for the races.