Yes we will still trade with Europe, but everything we import from Europe will become more expensive as import duties and tariffs will now have to be paid.Whether we are in or out of Europe we will still trade with them, them with us. Maybe within the short term we may be worse off coming out of Europe, but I don't think so in the longer term.
Guess who will end up footing the bill? All of us.
My concern is will companies like Nissan for example stay in the UK if there is not a tariff free way into and out of Europe? I very much doubt it.