I didn't understand the 'The Port of Dover wants to build out into the sea' bit, given that the article later says 'Mr Bannister told the BBC that plans already existed to reclaim land in the port's western docks, for cargo use. Now, he is looking to speed up the project so the new area can be used to hold passengers when EES starts.'
Anyway, it sounds like Eastern Docks pax could be housed or processed in Western Docks:
https://www.bbc.co.uk/news/business-66711198. Needs must, I guess, but it raises the interesting questions of: how d'you get them in there and back out again?