Tech salaries in continental Europe are significantly lower than in the US or UK. Even the most highly developed economies like Germany and Denmark often provide 50% of what you might make in CA or NY for a similar role.
Nope. Eastern European brilliant minds would flock to London and get paid far lower salaries than they were worth. Ukranians, Lithuanians. The legacy of communist math is alive and well - they were generally better than any western european talent you could get and cheaper. They would always get the top jobs, but the regular influx of new blood meant salaries were stuck.
Baltic countries. Romania, Bulgaria. There was a lot of talent available from the old Iron Curtain. The only example I can think of were Ukrainians and Bielorussians and even then I met a few people from Belarus.