"What about the NI border?"
A valid concern, but one MP asked in one of the PM's questions, "who would build it"? and no one could say. The UK have committed to no hard boarder and the Republic of Ireland have said the same. So who is going to build it; it remains a mystery.
"A queue of lorries will clog the M 20 as even a short customs stop would be huge."
Again, you're speculating what might happen, One MP said recently we might choose to simply wave stuff through until a sensible solution can be found.
"Most of the £39 billion is legally due...."
There is some legal argument over that. Some legal argument I have read says, the EU is a rules based organisation and there are no rules covering fees to leave, therefore, nothing is due.
"Recent figures show that even on non EU immigration we have failed to control numbers over many years..."
I agree, immigration has not been controlled at all.
"The Bank of England Governor is surely a credible witness for the possible chaos? "
I don't agree. He's consistently got things wrong so there's no reason to believe his crystal ball is any better than all the other pundits guessing the future.
The Arctic does indeed seem pretty appealing right now :-)