Returning to the topic a bit more, I'd say the UK is princely positioned as a place you'd both have to get out of and get warning to do so.
If it ever came to it, US sites would be top of the list for being hit. There is a huge amount of targets, infrastructure, etc to destroy there.
Nobody, not even Russia would be focused on doing that AND hitting other countries in parallel. Hence the moment Russia/other aggressor attacks the US directly (e.g. Russian fighter planes sink a US destroyer in the Med) or the other way round, I'm immediately driving to North Norway. I'd bet there would be at least 24h to get out before strikes come to the UK. More likely a week.