Hi, 2 weeks ago, I drove from Germany and went over from Calais by PO ferries with a Flexiticket which allows a 4 hr period : earlier or later than designated time. Even if vaccinated one had to show proof of a Lateral flow test and since mine was in German rather than the required Fr or English, you could do this at the port for 30€. ( 4 weeks previously the German proof had been accepted !) Before travel, I had to pre book my day2 test ( I did Boots) and the Passenger Locator form through the GovUk/travel site ( which no-one ever checked, but…
Coming back to France , you don’t need to test if vaccinated although one still has to fill in some form from the same gov site : Déclaration de L‘Honneur or something- where you pledge that as far as you know, you don‘t have the dreaded disease, However, when talking with the Very few people on the ferry, none had done or even knew about this form !
( If for any reason there are changes and you need to do a test in England - not the day 2 one, use the C19 testing by Cerulean Health. Cheap and so efficient.)
Really, nothing to worry about, so enjoy .
Anna