The plan is this Saturday I take a train to Exeter to see the chaps at Berrybrook Morgan to collect a new to me 2012 three wheeler. Never had any Morgan before. Then to drive it back with my teenage daughter in the passenger seat home on the Hampshire Surrey borders. Now the forecast does not look great and it is about 150 miles which normally I would do on the motorways.
I would take the A303 rather than M5 M4 although its nearly a motorway

You could stop off at the Haynes Motor Museum for a break. Maybe a bit of M3 or A30 at the end depending on where you ending up...
I suspect the A30 etc would be too slow, and you dont want to be sightseeing on a delivery journey!
Ensure you have a recovery service just in case and of course a backup battery for your phone(s) - that is just being an eeyoye but good for Murphys Law avoidance. Keep a small towel or cloth in the car for wiping your helmet visor / goggles / aeroscreens / windscreen. Golf brolly in case you get stuck in a jam somewhere (will fit in the passenger footwell). Ear plugs maybe. Agree a hand signal protocol with your passenger. Enjoy (and welcome!).