The caveat is that he was located in Nottingham for most of the history covered in the post, so this isn't necessarily comparable to SF -- more like, say, Colorado. That said, the most recent London (edit: sorry, Remote) salary is what I'd ballpark as average in London at the moment for that sort of position. There's been significant inflation in developer salary in London over the last few years, £100k is a reasonable total compensation for someone senior today. The salaries here are absolutely lower than in the US in raw numbers but in terms of overall position relative to other earners and quality of life, it's not much different.
The biggest gulf between the UK and US is at the top end, i.e: people earning TC of 500k+ is not uncommon in SF whereas that would be quite rare here outside of the upper echelons of the big tech companies. Part of this is because stock grants are much lower here in general, but salaries are lower too.
If you were an experienced software engineer in London today looking to maximise your salary, you'd have an easy time reaching £100k and you could probably touch £150k but it would take some effort.