I live near Bude, James. Weather has taken a turn the last few days and been a bit damp and blow-ey out on the roads. I don't really ride much MTB but there are plenty of trails in nearby woods and the moors are easy accessible. I'd pop into southfork in town (bude) for a bit of local knowledge on the MTB scene. They go out weekly if you fancied a group venture.
If you bring the road bike, i'd recommend heading out to widemouth bay and pick up the coast road to milook> crackington> boscastle, then up to camelford and onto bodmin moor. from there you can head back to warbstow, week st mary and back to bude. mood depending it's easily extended by heading further down coast towards port isaac, or by heading more south once your up on the moors and exploring a bit... milook is a bit of a burner (25-30%er) but great views, so worth tasting breakfast again for. If you wanted a pleasant coastal descent and climb, boscastle is the nicest.
bude>stratton>bradworthy>east/west putford> langtree> torrington (can go traffic free on the tarka trail if you fancy)>hatherleigh>holsworthy is a nice (90-100k'ish) road route for a bit of a pacier affair. or head to sheepwash after torrington for more quiet country lanes.
exmoor is great, as is dartmoor if you can get a car to up to them to do a loop, plenty of stuff online.
widemouth> marhamchurch> week st mary> canworthy> maxworthy> north tamerton> holsworthy> bradworthy> shop> duckpool> stibb is a good loop from bude.
duckpool is a great spot in coombe valley, lovely walking round there, hawkers hut, et al.
essentially, just avoid (as much as possible) the a39 either side and you'll have some nice riding.