Silicon Valley is a destination for immigrant tech workers
Silicon Valley is very cosmopolitan because of decades of influx of immigrant tech workers... Europe, Iran back in the day, more recently Taiwan, Korea, and of course India and China. Nowhere else in the US matches that with temperate weather. Seattle ain't bad, but "the skies... they be grey!".
Glassdoor: "The average Google hourly pay ... $201 per hour for a Senior Software Engineer.".
What's the UK going to offer to compete?