In reply to CPH:
Currently in France and due back on Tuesday, Dover Calais ferry both ways.
I was concerned about queues for the border checks due to our mix of citizenship, but the single queue for all four cars in it was no problem. Paperwork preparation was quite stressful, but the French border guard asked if we were all vaccinated and as soon as she saw my clipboard with paperwork prepared, said it was fine without even looking at it.
In terms of the French COVID App - https://bonjour.tousanticovid.gouv.fr , it is easy to use to upload NHS COVID certificates and WILL be required to get into restaurants (Terrace included), larger centre commercials and museums, etc. At one Centre Commercial, the QR code wouldn't scan properly, but the security guard let us in anyway. Masks are compulsory in supermarkets and EVERYONE wears one, perhaps they don't have any asthmatics in France or any other reason not to wear one.
For the tests coming back you can find your local testing labs on this website: https://www.sante.fr/cf/carte-depistage-covid.html . You can book an appointment online, there is a fixed national price for PCR and Antigen (LFT). Note, many do not do weekend appointments and not all do Antigen tests.
You won't be able to use your NHS LFT as proof of being negative for the return as the reporting website won't work if are attempting to use it whilst in France (I have just this moment tried to do so).
I still have the joys of the UK Border Force for the return and hope UK customs don't go looking for our stashed confit de canard.
Didn't see any sign of migrant activity on the way out for the first time in many years, but did see two porpoises in the Channel for the first time in 26 years of doing the crossing.