'German Cars' - again.
The UK is an important market for German cars, but not anything like as important as the UK likes to think.
VW sells 10 million vehicles a year worldwide - only 250,000 of which are sold in the UK, so less than 3% of annual sales. VW sells 4 million vehicles a year in China alone - the same China that the Brexiters claim the UK cannot sell to because of the EU. After Brexit, VW will continue to sell to the UK - the cars will just cost the customer 10% more.
Mercedes and BMW sell less than 10% of their production to the UK. People who want a Mercedes or BMW will still buy one after Brexit - the car will just cost 10% more. These customers are not going to start buying a Hindustan Ambassador instead.
If you don't want to buy a German car, your options are almost entirely cars built in other EU countries - Fiat, Renault, Peugeot, Opel/Vauxhall, Skoda are obviously European cars, but so are Kia, Toyota and Hyundai, which are built in Slovakia, Poland and Czech Republic for the European market. Once Jaguar/Land Rover, Mini, Nissan and Honda relocate, almost all cars sold in the UK will be from the EU. Even Jeeps are built by their owners, Fiat.
EU manufacturers will lose some sales to the UK, but will actually gain overall if the UK car assembly plants are relocated. The UK however loses one of the major exporting industries and 200,000 people will lose their jobs.
Now repeat for aerospace, chemicals, machine tools, food and drink - the EU loses a bit of their market; the UK risks losing a whole lot. But why worry - Minford, Rees-Mogg and Raab think it's alright for UK manufacturing and agriculture to be destroyed. It's a price worth paying - apparently.