Leaving the EU will not be the end of the world. Look at the closest countries that are not members either: Iceland, Norway, Switzerland, Liechtenstein, Canada. All of them are quite livable places.

Get serious. The total number of card-payed consumer purchases has peak hours of approx 500 transactions per second in my country alone. Nobody is going to have their mobile phone mine blocks at that rate all day long. It is going to be offloaded to a provider that will sort out all the transactions and keep track of your assets. If that isn't a bank, then what is?