Well, we made it back. For those who have not yet experienced it, it may be helpful to have a bit of advice on how to manage it (or not).
First, you have to pre-order your COVID test when you get back. We did this through a company called Randox (https://covid.randoxhealth.com/basket). I think they cost £48 each.
Next, you have to fill up a passenger locator form, not straightforward (Fill in your passenger locator form – GOV.UK (www.gov.uk)). It asks you if you want to open an account and when you enter your email address (I have three) it rejects it. Instead, you have to spot that at the bottom of the page there is a link to opening an account. It requires a fourteen letter/digit password (ie one which it is impossible to remember), nearly twice as long as most other passwords. I’m still not sure I filled it up correctly. Nor was the very nice and helpful (French) official who had to approve it at Calais.
Then, most tricky, particularly if you are in a small Provençal village, you have to get an approved COVID test. It has to be done at least 48 hours before travelling which, for us, was the day we arrived. The French government provides a map of approved testing places (https://www.sante.fr/cf/carte-depistage-covid.html). There were several in Draguignan. They appeared to be closed at the weekend. So, we decided to be tested this morning in Dijon. The only problem was that the approved testing place said they would give us the result tomorrow. Eventually, we found a very helpful pharmacist, not on the approved list, willing to do it. She stuck the poker so far up our nose that we all three screamed in turn. The test is no different from the one we routinely do ourselves, apart from how far into the sinuses the poker can go. On the way out, you fill up a form saying you have tested negative. But on the way back the British government no longer trusts you and requires a French pharmacist to produce a certificate confirming you have tested negative.
Bonne chance !