Honiton, where the 200 and 300 (VOR & Old Roads) start, is not much further to travel. Cheap advance trains from SW Trains. There is a campsite, ask Hillbilly for details.
As for the Brimstone - I'm sure you will not be disappointed. There are many 'cheeky little (and not so little) climbs, of course, but judging from my perm experience last year, if you made it round the Porkers ok, all things being equal you should not fret - just enjoy the weekend.