This is one of the truly fabulous consequences of the Schengen area. It's possible to end up in another country by accident, no passports involved.
C. drove the whole time, UK car on continental roads. Despite driving on an unaccustomed side of the road, he astonished both of us by making absolutely no mistakes about which side of the road he was driving on. We figure he'll be overdue for one if we ever do another continental road trip.
My biggest moment of relief: checking in to the last hotel and confirming I'd made all the hotel arrangements for all the correct nights.
We had some really good places to stay on this trip, including the decadent B&B near Amiens, complete with dinner and good company; one night on a houseboat-hotel in Ghent; one night in a hotel which only opened a week-and-a-half before we stayed there, newly-built (and thus hardly anyone else was staying there); and one night of complete luxury in a countryside chateau with really, really good food and service. Also, this was the trip built around me winning free lunch in the French countryside in the Menu for Hope raffle back in January. (More on many of these things in the near future.)
P.S. Pretty much all my online time on this trip went to my students, so I will never know what urgent things happened to my f'list in the past fortnight unless you let me know.