It isn't my contention though, is it? It's the contention of leading authorities from every major sector of the UK economy, almost every leading economist, etc etc etc. The simple fact is that No Deal will be seriously harmful to the UK's economy, and that's only in the best case.
As to the argument that "the consumer has the choice", fair enough, but given a choice between expensive British and cheap foreign, people will opt for cheap foreign. And if the UK industries -- farming, in particular -- respond to that by lowering their prices, then they *still* suffer. Perhaps this is because the UK business structure has become too heavily dependent on EU membership, but even if that is the case, then the solution is not to rip the EU band-aid off in a flash. All that does is lead to heavy bleeding. That's the reason that, if Johnson's deal passes, then the first part of it is deliberately a one-year or more period in which almost nothing changes.