Well, I am not in the UK I live in OZ and I am 76 years old I have not used cash for a number of years, were ever I go, I pay by debit tap and go card except when I go to Thailand for holidays, I take cash which I withdraw at the local ATM in my city because I get a better exchange rate in Thailand than I get in my country. So, I am cash less.
Yes, you can go overseas for short trips I am not sure the correct days, but I think it is 10-14 days I did, and it did not affect my 2 years waiting time