But we would have access to the Single Market, just not be a member of it. In the forthcoming negotiations, the EU will insist that when we sell into the Single Market, we comply with product regulations, and financial services would have to comply with relevant regulations etc All this is relatively simple for the UK, which has been a member and has complied until now. No great changes will have to be made.
A deal will be struck with the EU. How beneficial to the UK depends, it seems to me, on how damaging to EU member firms the introduction of tariffs is to their exports to the UK and also the need of EU industry to have unencumbered access to finance in the City of London. A number of EU member states are in a parlous state re their economies (Italy, Spain, Greece etc), so the idea that they will be prepared to damage their economies further just because civil servants in Brussels feel the need to punish the UK is simply counter intuitive. Add to that the need for British Defence capabilities in the face of an increasing threat from Russia and the possibility that without a deal, the UK might drop its corporation tax to Ireland levels to encourage investment, and it's clear the EU has a lot to lose if no deal is struck. Pragmatism will prevail, and this is the noise coming from Angela Merkel.