This was mine for London to Cornwall (I only got as far as Honiton as I was tired, soaked thanks to headwind and driving rain and was going to be later than expected).
(It would help if I added the bikely link!):
http://www.bikely.com/maps/bike-path/143181
Some important notes:-
1. This was for a DIY 400 Audax so I had to route it through some towns to get proof of passage, but this does allow for some coffee/food stops along the way. My controls were (I think): Putney, Alton, Salisbury, Shaftesbury, Crewkerne, Exeter, Tavistock, Liskeard, Padstow. I started at 10am and AUK rules gave me about 30 hours to do the ride meaning a 4pm deadline for finishing the day after. I was planning on getting to Dartmoor at dawn so I didn't have to ride through that spooky place in the dark. Any time in hand was going to be spent sleeping at my parents house in Dorset.
2. Don't take the suggested little track between Crondall and Well. The OS map may have it down as a "single track road with passing places" but it's actually a stream with a rocky bed. Nice walk though but my feet were a bit damp afterwards.
3. The detour at Crewkerne was to drop in to see my parents for food and a shower. I'd just carry on along the A30 as they won't be as happy to see a random person turning up. Plus they'd just had some floor tiling done in the bathroom and the kitchen so I couldn't use either. Great.
4. It starts to get really hilly approaching Chard.
5. Dartmoor, but not a problem for you as you'd probably turn off this route at Honiton and head towards Tiverton and then Barnstaple.
6. Devon / Cornwall. The latter will only be a problem if you go seriously off route.
7. The wind in the UK is predominantly a South-Westerly. Expect and plan for a headwind the entire way.
8. The A30 is surprisingly nice to cycle along as most of the cars going that way will be on the A303 or M4, but there are some busy-ish sections.
I'm planning on doing this again in late May and making it the whole way this time.
