Should London get nuked (and there is zero chance of that happening), I'd move to North America (Seattle?), or Sweden (Stockholm), or Canada (Vancouver). Seattle because it's nice, and has potential... Sweden because Lucifer rose there in the last decade , and may do so again, or Vancouver because I'm feeling out of touch with Chinese people, and Canada is the closest "match" culturally to the UK, whilst still having the splendour (and some of the wealth) of North America.
But imagine losing London... the mass of people, the complete devestation, the center of everything in the UK, business, social life, organisation. No more Slimelight, Camden Town, goths, punks, ruthless businessmen (I have a soft spot for those). The resulting crises would be unsurmountable, and Slimelight would not rise again.
Morbid thoughts today :-), but out of fun, thank fate, rather than actual fear.