[pjc50]

Even if the UK decides to accept fraud and have a customs-free border, shipping is bi-directional; once the tailbacks start, lorries start parking up on the M20. Drivers are going to be reluctant to cross the channel if they can't get back again in a timely fashion.

(Are EU truck licenses valid in the UK after Brexit? And vice versa? Who knows?)

[trocadero]

The issues you mentioned are relatively minor. Drivers will still cross if they are paid enough. The UK can easily recognize EU truck licenses on their own. Undoubtably Brexit will cause some disruption to UK/EU trade, but it's pretty far fetched that it will completely break down.