Take the A3079 out of Okehampton, a good stretch of road with some good straights and tricky bends.
Take the B377 from Exeter to Crediton this first bit is quite boring but after crediton the road gets Interesting. Then from Crediton to barnstaple (beware of a bad right hand bend about a mile out of copplestone.
All the way to Bude, another good road.
A nice route with good scenary, not super fast but interesting anyway. Can be busy during holiday season as it so picturesque.