I am amazed at how the media still go on and on about future trade, just as Remain wishes them to do. Remain wishes to muddy the water. Most countries trade just fine with each other under WTO rules. The average world tariff under WTO rules is now very low, and considerably lower than the costs of EU membership as a proportion of our EU trade.
More importantly Remain can never answer the question what new barriers do the rest of the EU want to impose on their trade with us, given that they sell us so much more than we sell them. By what mechanism would they be able to impose new barriers? How do they get the changes through? How do 27 other countries decide new barriers? How do they impose them unilaterally without us retaliating? What barriers could they agree that are compatible with their and our membership of the WTO?
The Remain issue seems to have narrowed now to the question of passports. Most Remainians now seem to accept that Germany and the others will not wish to face a 10 % tariff on exporting their cars, so they have shifted to services. All the main banks that say they are worried about the passport have subsidiaries in other EU states, so after Brexit they can use one of their subsidiaries to route service around the EU whilst still doing much of the work in London as they do at the moment. The most popular of all the passported products, mentioned in the government publication is the UCITS fund. Most of these are based in Luxembourg or Dublin any way so Brexit will make no difference to their domicile.
What the Remainians seem to forget is the current arrangements for our trade remain in place unless and until they are amended. It is best to amend them by mutual agreement. If the rest of the EU wishes to amend the current tariffs and non tariff barriers in an adverse direction without our agreement they need to make sure they do not infringe World Trade Organisation rules in doing so, as they are bound by them as we will be on exit. They will also need to remember that if they vary them adversely to us unilaterally then we can vary them adversely to them unilaterally, subject to WTO limits on both sides. They have rather more at risk, as the higher tariff of 10% on cars is permissible under WTO rules, whereas most other products are limited to much lower tariffs. The UK has no wish to impose new tariffs and barriers on the rest of the EU despite being a heavy importer, and assumes the rest of the EU will come to the same view as they export so much to us.