Considering many people who design and develop the tech for robots in the UK are migrants, i don't think this strategy will fare particularly well
If I understand UK visa rules correctly, getting a work permit as someone who designs or develops tech for robots is as easy as getting a job offer from a company that wants you to design or develop tech for robots for them.
1.) This doesn't help startups -- only large companies that can afford to go through the expensive and laborious visa-permit process.
2.) As a foreign worker, since your residency depends on employment, you're in a far worse bargaining position vis-a-vis salaries, so this depresses worker wages, however much the government tries to enforce the requirement that foreign workers are paid at prevailing wages.
3.) Also because your residency depends on ongoing employment, putting down roots and becoming a full-fledged member of the community is much more difficult.
Source: I'm a non-EU immigrant to the UK, brought in specifically to work on automated transport technologies. The hacks I've had to go through to start my two companies here are unbelievable. The UK's immigration policies are seriously bad at attracting talent, and post-Brexit, look like they'll get much, much worse.