I don't think anyone commutes from the Home Counties to a job at Pret. People on lower income still live in London, just in not as great housing. People on the train are people who can afford the choice of a luxury of a home in a village or the countryside instead of London.
The "Stockbroker Belt" is a thing, and Sir Humphrey used to commute in from Haslemere (if only fictionally, but I'm sure he was based on real examples).
I don't think anyone commutes from the Home Counties to a job at Pret. People on lower income still live in London, just in not as great housing. People on the train are people who can afford the choice of a luxury of a home in a village or the countryside instead of London.