Pompey.

Franglais:
Services Rownhams North, on the M27 has an advice point and COVID test point.

M275 Portsmouth Park and Ride is the inspection point you must enter before going into Pompey Ferry Port, either to ship yourself, or to drop a trailer that is shipping. (Channel Island traffic not affected though) No COVID tests here, they just do checks to ensure you don`t go to port and clog it all up if owt is wrong.

A31, I don`t know about.

If you get a docs’ check at, for example Rownhams services, and the Advice Point tell you your docs’ are good. Do you get a “Docs’ are Good certificate” to show at the M275 Park and Ride Inspection Point? (So that that bit is an in and out job)
I suppose you’ll also get a dated and timed COVID Free ticket. The test takes, I believe, around 15 minutes to test, so you might as well get your docs’ checked while you wait. But if you have to go through the whole docs check rigmarole again at the inspection point, is there any point in going to an advice point, other than peace of mind?

I haven’t been over the water yet this year. I haven’t had a chance to talk to our drivers who have either.
We don’t use Dover - Calais, but do go down through Eastern France to Basel.
The boss is very thorough with paperwork, so I wouldn’t expect problems, however errors can slide in, never say never.