The Silicon Roundabout/Tech startup scene is mostly for staying:
http://techcrunch.com/2016/02/24/sho...r-should-i-go/
It's an industry that is especially 'European' in London and one which would need to be able to recruit from across Europe irrespective of the result of the referendum.
How will quickly will they be able to hire EU citizens?
How easy can EU citizens setup companies in London?
What happens to Fintech startups (like this
one founded by EU, not British, citizens) which benefit from the open market in services across the EU?