But we do see the same problem in several European cities. For instance there's been some debate about how nurses can't really afford to live in Oslo anymore due to the discrepancy between income and rent.
Probably many delay having a family and are able to share a house, but eventually that's going to get old for a lot of people.
So no, the baristas, janitors, etc of London can't live in London. But at least most of their commutes aren't as terrible as the majority of US workers driving individual cars over great distances every day to go to work.