Pounds changed 5/6 yrs ago as we learned LOL . No one would take old paper bills. BOA really would of had us in a pickle if we didn’t have
credit cards. People reacted as if old bills where phoney money. Free to exchange in post office old for new. If you had an account in a British bank they also exchanged them. We arrived on a Sat evening banks and post office closed till Tues . There was a bank holiday . Our Bellman at hotel exchanged some personally till Tues so we had some pocket money.
Tap card and go was everywhere so really cash was obsolete. We do like to tip cash even when paying with card so bellman’s exchange helped the service people we encountered. Cabs,Barmen.waitstaff Tour guides etc