At a FAANG you can get ~£200k per year in London at a Senior level. Deliveroo doesn't pay particularly well (even though it's meant to be a competitor to Doordash which afaik does pay well). The Cabinet Office is a governmental agency and I would say it pays pretty poorly for London, but you'd probably find the same in the US.
You can get a better sense of the salaries in the UK via https://www.levels.fyi/t/software-engineer/locations/london-...