Get real. Nearly half of our export trade is with the EU and without a trade deal our exports will be subject to tariffs making them more expensive at point of use in the EU. If there are other ready markets out there that we can steam into to take up the slack why aren't we already doing this? Some are talking about the glorious opportunities in Commonwealth markets but Commonwealth Preference Tariffs were scrapped decades ago so that argument is even more redundant than it was 40 years ago when others with a similarly tenuous grip on reality were putting it forward during the 1975 Common Market referendum.
As for your argumment about the effects of Brexit on immigration, below is part of my post from yesterday.
"....., the situation in the 'Jungle' in Calais is that, as part of cross border co-operation within the EU, the French authorities are committed to do their best to prevent these people (and any others) from illegal access to the UK. There is also a British police presence in Calais to monitor the situation and co-operate with the French. Calais is therefore effectively our border. If we leave the EU the French police will wash their hands of the migrant issue in Calais and no longer prevent anyone from attempting to enter the UK illegally as it would no longer be either their problem or their responsibility. The British police contingent would also have to be withdrawn. This would mean open season for illegal migrants and the couple of recent instances of boats full of them caught crossing the Channel would increase exponentially and northern France would become a magnet for many more migrants trying to enter the UK illegally."
Wouldn't the people of Calais and northern France have a strong incentive to stop the area from becoming a magnet for migrants trying to cross to the UK?