I traveled back through calais port to dover on the 28th of Dec just gone...french immigration officer said we might have trouble with the brits as it must be essential travel for ,told her we were going home through the UK and heading straight to the ferry in hoyhead...
UK immigration only checked our passports and waved us on,no problem at all...same in dover,just waved us on,we had the UK locator form filled out though which stated we were except from getting a test in the UK as we were transiting by land....all info is on the UK government website about transiting UK by Air and sea.