For those wanting specifics: for a mid-level Python gig at a large investment bank, base of 80K GBP, bonus between 20 and 40K GBP, expecting base to rise accordingly over successive years.

However expectation was 10 hour and 12 hour days, and work environment seemed, for want of a better term, hierarchically abusive.

Furthermore, anyone who's seriously good is contracting, which should net you around 5-600GBP/day.

I suppose also consider rent in London is like 4x rent in other cities (or so I'm told).

It's expensive, but relative too. Last time I ran the numbers London was was more like 1.4x Paris, but it might be 4x somewhere in rural Wales...