Some of that looks familar
Day 1 Hills! You may be able to cross the River Fal using the Philleigh - Trelissick ferry as per the
Kernow & Southwest 600.
At 192 km would you not be better of using Higher Rd on the approach to Crediton?
Day 2 I don't know what the main road after Avonmouth (109 km) is like, but my way through that maze was slow & some of the NCN was awful, possibly the worst section was at 118 km on your route, where you have no choice.
Everyone says use the eastern side of the Severn Bridge as it avoids a tunnel filled with glass.
The approach to Hereford on the A49 wasn't good (lots of fast traffic) which is why I cut through Callow and Grafton (177 - 181 km)
At 216 km you can shave a bit off you route by going through Orleton along Kitchen Hill Rd.
Day 3 I used the Warburton toll bridge to cross the Manchester Ship Canal & to avoid central Warrington (tho I see you are on some sort of cycle path).
Your approach to Warrington (143 - 144 km) could be very busy.
Pippa found a better route to the Warburton toll bridge then I did, see her route
here:click.
It may be quicker to avoid the centre of Wigan & go westwards on B5206 through Billinge & Orrell.
The cycle path through Preston is decent.
Day 4 Get ready for dullness between Gretna & Moffat as you parallel the M76.
Day 5 I like the
By The Way hostel in Tyndrum, but that's a few km further north than Crianlarich.
Day 6 I've never cycled over Rannoch Moor (the road into Glen Coe) but have driven it loads of times. If I were to cycle it I'd want to be in Glen Coe by 7am because it gets very busy.
Day 7 People told me the Struie Road (your first 25 km) can get busy, but I didn't have any issues.
Make sure to stop at the Crask Inn!
Ride out to Duncansby Head lighthouse, it's far more peaceful than finishing at the signpost (& is further from Land's End!).