Topic’s been done a few times, but yes there’s plenty more than the official stuff. The official stuff though, mix the blue in with the red. Not gnarly but if you go at a quiet time when there are no families along it the blue can be a fast blast. The red is too short really and the black is a joke.
Off piste there’s some nice stuff about. It’s not amazing and I wouldn’t make a special trip of it, but nice if you’re in the area.
I’d also look at Woodbury Common over by Exmouth, though it’s natural trail stuff, mix of xc, singletrack and a little jump area. Nice scenery though. Dartmoor has a fair bit of natural gnar. If you want to step it up, then head to Gawton.