I'm pretty sure it would be targeted just like every other state. The world would be covered in nuclear Fallout so it doesn't matter. You either get lucky and survive, die, or turn into a ghoul. 99% chance of death I'd say.
Its not the fallout really that you need to worry about - that goes down to safe levels after a couple of weeks.
Its everything else that you need to worrry about - The entire UK healthcare system if concentrated into one place would not be enough to deal with the aftermath in one UK city. The number of non-nuclear injuries (that is stuff thats not specific to a nuclear blast) would be so great there would be no chance of the system coping; plus your entire food supply chain has been eliminated, etc.