I expect a no deal brexit would create barriers for trade between Europe and the EU. This would hurt people on both sides of the trade.
It's not like one side benefits - say the EU has a tariff on UK goods, who wins? Neither. People in the EU pay more for UK goods and people in the UK can't sell things to the EU. Same thing for the movement of peopole - Europeans "lose" because they can't visit the UK - the UK "loses" because they don't have people from the EU visiting.
The real action on this to my point of mind isn't economic that, in my view, is simple. The action is political - in terms of how much sovereignty the UK wants to hold on to and how eager the EU is to discourage other members from leaving.