But if they are actually stupid enough to do that they'll have made an enemy of an economy much larger than theirs, their largest export market, a country they're heavily dependent on for the basic infrastructure of running a government...
I have no dog in this fight (not that it's not entertaining theatre), but I also know that capitalists have very few enemies they will not sell to. If they were willing to deal with tinpot Central American dictators, you know they'll have no issue whatsoever in dealing with the Scots. You're probably overestimating the actual level of dislike between Britain and Scotland, even in the face of divorce. And you're especially overestimating the dislike of bankers cozying up to whomever they can make a profitable deal with - sharks have no national loyalties.
That being said, if the Scots really wanted to piss off the British, they could apply to France to become a protectorate and then keep the nukes.