UK residents if travelling abroad and wish to use the local currency can buy this easily at overseas ATM's and banks using their credit cards , debit cards or travel cards.
Foreign visitors and workers from abroad can use their credit cards and debit cards in the UK.
Workers from abroad can be issued with re-loadable debit cards by their employer . These cards do not need to be supported by a bank nor is a bank account in the UK needed.
Euros, Dollars and any other foreign currency would not be accepted in the UK after 31st December 2020.