The EU will remain our biggest trading partner for a very long time, by shear gravity. We'll have to accept or follow EU standards on goods, H&S, state aids etc or stay close to it - there is a scope for variation but by and large, we'd have to stick to EU's standards anyway.
You need to think in terms of macro-economics. External trade is important but it's a smaller part of the economy and we'll continue to trade, deal or no deal. Don't get too hung up on GDP growth and and tax revenue that would have been if we were to remain. We'll leave but gravity will keep up in close orbit like the moon and earth.
While there is some truth in your comments, I think you continue to underestimate the scale of the problem which will only begin to become apparent following our exit from the EU, should that come to pass.
Many dispassionate commentators have previously debunked the notion that we have aces to play in the ongoing negotiations so I'm at a loss to see how we can possibly expect to reach any kind of deal that isn't painful and punitive because the EU has always held all the aces. May's got her head so far up her backside that she has lost touch with reality and it has become clear that she simply doesn't have the talent, guile or charisma to impress foreign leaders, as witnessed on her current jolly abroad.
We need them a whole lot more than they need us and anyone who imagines that corporate Germany and France will soften up for fear of losing the UK as a large trade outlet is living in cloud cuckoo land.
Those two major players, not to mention Italy, Spain, Portugal and all the more recent entrants into the EU will happily accommodate the large companies which will exit the UK during the next few years if 'Brexit' is not stopped.
Currently, there are many car manufacturing plants in the UK but of those, only a few are British-owned. I believe that Honda, Toyota and Nissan will pull out within the next two to three years as their corporate interests will be better served elsewhere. That will add enormously to this nation's welfare bill.
As we cannot produce sufficient food to satisfy demand within the UK, we will need to import lots of produce from wherever we can get it but it won't be cheap. Food, medicines, space and aviation research projects will cause us major problems and of course, the banking operations in the City and at Canary Wharf will be easily dispersed to venues in mainland Europe.
This is the position in regard to the carmaking industry as of late last year:
https://www.theaa.com/car-buying/cars-made-in-britain
Tom
