According to levels.fyi London is basically the best paying non-US city, I think maybe beaten by some Swiss cities.

I've always found levels.fyi to be a little pessimistic for the UK when compared with commercially-available benchmarking services.

I suspect it's because people on PAYE tend to think of their basic salary + bonus + income tax, but disregard NICS, pension, paid holidays, and other benefits. They end up reporting a total package that's 10-20% lower than it actually is.