“even with a succesful out vote full trade will continue in and with the europe zone”
Actually France has made it clear that that will not be the case unless the UK does what Norway does and adheres to EU rulings on a host of issues — while having no influence into those rulings. Basically, if the UK leaves, it has two choices:
1) accepting precisely the things it hates about the EU while losing all the leverage it might have from staying in, or
2) losing all its markets in other European countries, losing London’s status as the financial capital of Europe, losing the renumeration from UK citizens working in other EU countries as they will be fired and deported, and probably losing Scotland as well