The problem is that these same people all came to the conclusion that on voting Leave, during the negotiation period the UK would lose 500,000 - 800,000 jobs and enter a massive recession caused by "uncertainty".

The UK has since hit the lowest levels of unemployment on record and economic growth is outstripping Germany, France and Italy.

Economists have no credibility with regards to Brexit. None. They have less than zero credibility in fact: if they're saying something, it's a good sign the reality is the opposite.

Thus the idea that no deal would be bad for the UK is a deeply suspect one. There are many things the UK can do outside the EU that would accelerate growth even further still, according to conventional economics. But regardless of what you personally believe, at this point it's just guessing - your views have no more legitimacy than the views of people who think any sort of deal with the EU is bound to be harmful to the country and its prosperity.