I have a feeling that because of the peculiar way french retail works with everything being franchised to regional owners/ coops, the drive is an entirely separate centrally owned operation from the bricks and mortar stores so there could well be quirks with the online side that have no bearing to card present transactions in stores. Quite a number of ecomm sites will try to force either a french BIN or a french billing address, partly as a fraud prevention measure and partly to try and avoid any extra charges that could be levied from non EU cards, so I could potentially see a situation where ordering things online, including via drive sites, gets more difficult. I can’t see mass UK card refusals happening anytime soon but people did warn some time ago that there was a real possibility, if unlikely, that using UK issued cards could get more expensive in the EU, but of course if there’s one thing we’ve all learnt about brexit, then continued with the UK response to Covid it’s that the UK has heard more than enough from experts who know what their talking about and prefers to listen to conspiracy nutters or gammons who talk about taking back control every other sentence instead these days.