Brexit: What are the rules on driving in the EU after transition?
https://www.bbc.co.uk/news/uk-47459859Most of this has been covered on GGi a while back, but not, I think, this bit:
The rules for GB stickers are that you need one unless your number plate has GB on it, either alone or alongside a union flag. If the GB is alongside an EU flag or the flag of England, Scotland or Wales then you still need a GB sticker.