You will need a UK sticker, doesn't necessarily have to be on the number plate, it was Boris's idea to emphasise the countries unity after Brexit ???
https://www.brittany-ferries.co.uk/...ion/do-i-need-a-uk-sticker-on-my-vehicleTo comply with the law we put a UK sticker on but I see many people still using the GB sign either out of ignorance or defiance. Not worth rubbing the Gendarmes up the wrong way for the sake of a sticker.