I'll be driving in my Land Rover 110, with a roof-rack, leaving Ste-Marie-de-Gosse on the 22nd October and returning on 5th November ferry (Dieppe - Newhaven - Brighton - return).
I have a spare seat (plus one very small one in the middle, but not ideal) and you will need bring a tent or book into a b&b as I'll be stopping overnight so as to arrive in Dieppe the eve of the 23rd and taking the 5:30am ferry on the 24th (yuck!).
I do have a dog, but he's no problem. I will be travelling back with a trailer and building materials though I will have plenty of room both journeys, if anyone needs something bringing back or taking to UK.
It would be great to share the driving but not essential.