As Nigel B said:
The 100 or so miles from near Dorchester to the M5 took 3 1/2 hours.
Never again ! If I can't get the ferry again next year then I'm staying at home & day tripping locally.
I've been looking on the official U.K. and the French websites to check on requirements for going out in my motorhome to France on the Newhaven - Dieppe ferry and for when returning but I lost the will to live after an hour......... neg tests within 72 hrs outward and return......booking day 2 and day 8 PCR tests (at between £80 and £140 each) for when back, a signed 'Declaration d'honneur' and it seems to require a QR code (whatever that is) and a vaccination certificate carried on an iPhone (which I don't have).
Sod it, I say.