How are you tackling the Land's End to Okehampton leg?
I guess it depends on whether your LEJOG is intended to be a roving jaunt through the countyside, or a slog to the finish, but we hit the A30 all day. If you're looking for a slog to the finish then it's perfect, but if not then steer well clear. It's ridiculously busy, with lots of fast moving trucks, and there are some sections where it becomes a single carriageway and quite hairy. The day we did it, the weather was almost identical to this weekend, i.e. amongst the hottest you've seen in this country, and combined with the constant rolling hills, I must admit I found it a very tough day. Bear in mind that some of the hills on the A road are tough, so expect worse if tackling the lanes.
Our second day was also to Bristol. We found Exeter pretty busy and tricky to navigate through but that was nothing compared to Bristol itself. We were very fortunate that we were passed by a friendly local cyclist who went out of his way to guide us through the city and help us find our B&B. We'd have been searching all night otherwise. There's a nasty hill just before you arrive at Bristol too, but a terrific descent afterwards.
Scooting further ahead, our day 6 was Penrith to Glasgow. We hopped onto the B7076 which tracks the M74 from Gretna to Hamilton. It's perfect for cycling along, we hardly saw a car the whole stretch, just smiled at the queues on the motorway as we sailed on. It's the route to take between Gretna, through Lockerbie and on to Moffat. Hamilton/Glasgow can be tricky to navigate through. We were very thankful we had the garmin at that point.
Once you get north of Glasgow however in my opinion you'll find some of the best scenery in the British Isles. Cycling past Loch Lomond we stayed on the A82 all the way to Fort William. Get ready for the descent to Glencoe, it'll leave your eyes streaming and wanting to climb back up to do it again!
Similarly, Fort William to Inverness is breath-taking. No need to Leave the A82 in my opinion, it's direct yet it takes you right along the banks of Loch Lochy and Loch Ness, and you pass the famous Commando Memorial on the way.
Good luck anyhow and let us know how you get on. I've practically blocked out all of the painful memories now and am getting itchy feet for another attempt!