At this level of compensation they would be competing with financial sector. I have not seen any evidence of this so far in London. I have not seen start-ups openly offer that kind of money so far. I think this is just a speculation from your side. Shame we don't have an AngelList.
I work at a venture capital fund so I've seen internal salary data from a number of tech startups as well as from recruiters in the space. I also used to run a developer recruitment startup which gave me access to a lot of internal data from hiring companies.
While it closes the gap with fintech, top devs at hedge funds can make £200-£300k (I have friends who are in this range) which it's hard for any tech startup to compete with.
FYI. AngelList are now operating in the UK and are ramping up. @andychung is their guy on the ground here.
