Tbf this is just this thing about the British society. I've lived here for 9 years and people are just not used to £50 notes, in several places I've had them refused(and I wasn't paying a £2 bill with a £50 note either, more like a £300 piece of jewelry and the shop just had a blank policy against accepting £50 notes, I've had this happen at petrol stations, at big stores, at small stores, people just don't like them). Where I'm from(Poland) high denomination banknotes are pretty common and no one seems to mind, I wouldn't have any qualms about paying for a 10PLN(~£2) item with a 200PLN(~£40) note, and I'm 100% certain that the seller wouldn't have any issue either. Meanwhile in the UK I was told by friends that if you're paying for £1 coffee with a £20 banknote you must be some kind of an inconsiderate dick. It's really weird to me.