Re: dress rehearsal
You've fallen into the trap. You say "we import" but in fact, it is "the EU import". We trade with the outside world under EU treaties. Those treaties allow for the easy importation of goods to the EU, and therefore to us. Once we are outside the EU we will not have those treaties in place and import/export, from everywhere, will become a lot more difficult. Best case is that we can renegotiate to get the same deal as we had in the EU. But we would have to do this on an individual basis with every country we trade with, and that takes time, and negotiators that we do not have. Worse case is we have to fallback to WTO tariffs - that is a very bad position to be in.