Our biggest bargaining chip is the significant amount of car manufacturing jobs that rely on British exports. I have a German branch of the family and before the referendum I was at a family event with said branch discussing what was going on in Port Talbot with a cousin of mine.
He basically told me that there are towns in Germany exactly like Port Talbot where 50% of the town works in one industry and the other 50% work as plumbers etc who rely almost exclusively on the other 50% for work. He was saying that he was hoping for a remain vote here as the ramifications of a Brexit vote would see a lot of these towns go under because Britain is by far the biggest importer of German cars. You must remember that during the run up the election scare stories about Brexit were rife including the line that us Brits would stop buying German cars.
The German government will not want to lose potentially their biggest non EU trading partner. With all due respect to other countries who may leave like Greece we are the United Kingdom, we have far more financial clout than others. This is why we will get a good post Brexit deal, the EU have far too much to lose.