No, we don't make much. 78% of UK GDP is from service industries, of which the financial services industry, based in London, is the biggest. Service industries include hospitality, tourism, education, prostitution (yes, really!), etc.
Motor vehicles are actually one of our biggest non-service exports BUT most of the companies are not British owned. Companies such as Nissan have chosen the UK as a manufacturing base, because we have access to EU markets.
There's a real possibility that companies such as Nissan will relocate if the UK leaves the EU. There's also a possibility that financial services will move to Frankfurt. As Germany is the UK's second biggest export market, I can't honestly see them making our life easier for exporting. It's more likely that they would put up trade barriers and seek suppliers in cheaper areas on their doorstep to the East.