I camped at Longbottom Farm at the weekend (known as Mendip Camp). Very basic facilities but a lovely spot, and open fires encouraged too. http://www.mendipcamp.co.uk
There was an 11 acre plot with large barn just before that campsite up for sale last year. Really wanted to buy it and build a new farmhouse with walker/cyclist camping only up at the top of the field with fantastic views. Guy wanted £200k and it is AONB so would have been a huge risk.
Never been up Brent Knoll, keep meaning to but will probably do Brean Down first.
There is a bridleway up the west side of Crook Peak but it’s a bit steep for going up and good and technical on the way down. There is technically no riding down the long diagonal (SE) but it is fun to do once or twice, just watch out for the warden, be considerate to walkers and stop in plenty of time as they have now fitted some fencing at the bottom which is very effective at stopping cyclists. More rewarding than the main decent is the bit just after the fence making your way down to the small parking area right by the corner of the road.
Heading east over Wavering down is a killer though and there is now a bridleway over the north edge of Shute Shelf over to the lillypool cafe and then onto the rest of the mendips. Good ride.