Whilst we are still part of the EU, the Eurostar will whisk direct to Brussels far faster than any ferry
18 months from now you'll need a visa and a very long wait to go Dover to Calais or Dunkirk, the other (nicer) option is Harwich to Hook.
How do you know that you will need a visa?
And why should the queues be that much worse?
And are you suggesting that the Eurostar will be in some way off-limits a no-no?
I am afraid Brains, despite your many good posts I find your post bizarre.
Hell, I travelled across Europe as a student with frontier checks all over the place.
And went into the old eastern block a few times - by plane and train - and don't remember any great problems.
Strangely I don't remember having to leave any trains and stand in cold railway sidings while men in frightening hats examined my papers. I seem to remember that stuff was looked at while the train rattled on.