"It's not in EU interests to cut their noses off too much either. For example, a big percentage of German cars are exported here." Not that old chestnut again.
Have you ever heard of supply chains?

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www.ft.com/content/c397f174-9205-11e6-a72e-b428cb934b78
while the final assembly of each Bentley remains in Britain, the components that make up the cars are drawn from across the world and often zigzag back and forth between factories in the UK and the continent before arriving at Crewe.
That leaves Bentley’s supply chain, in common with that of almost every other car manufacturer in Britain, at risk of being hit by tariffs if Britain leaves the European single market.
Bumpers for some Bentley Bentaygas, for example, are made in Europe but then sent to Crewe for inspection before then going to Germany for specialist painting. After that, they return to the UK for final assembly.
Another example of the interconnectedness of the supply chain is a fuel injector for diesel lorries manufactured by the US component maker Delphi.
This part uses steel from Europe which is machined in the UK before going to Germany for special heat treatment. The injector is then assembled at Delphi’s UK plant in Stonehouse, Gloucestershire, before being sold on to truckmakers based in Sweden, France or Germany.
If the resulting truck is sold into the UK market, the component or materials used in it will have crossed the Channel five times before the lorry is ever driven by the customer. If tariffs are applied at each stage, the cost could be substantial.
Suppliers to the UK car industry have warned that just the uncertainty over future trade agreements may force them to relocate parts of their manufacturing process overseas.
“If you have any tariffs, you would have to fundamentally look at your whole supply chain because you could quickly end up losing your margin on the component,” said Tim Lawrence, head of manufacturing at PA Consulting."
www.ft.com/content/c397f174-9205-11e6-a72e-b428cb934b78