Earlier quoted context omitted.
Calling it right now: give it five years, and even Raspberry Pi will be relocating. ARM is already somewhat relocating - some of their newest cores, like Cortex A78, were designed in Austin.
I don't think they'd relocate, but that doesn't matter. They most likely will pull an ARM and hire almost entirely in the US and India instead of in the UK, because competitive British engineers would immigrate to the States, and you can get top tier Indian chip design talent across the spectrum for $30-60k.
I just don't think this is very true, some perhaps but not many.
Secondly, if "the salleries are too low in the UK" is the argument then why would companies be interested in shifting hiring to the states?