OFO,
I'd be interested to know how the SNP would manage to get rid of the UK's deterrent. Are they likely to win the next general election in Westminster then? Even if they closed all RN and RAF bases in Scotland, I doubt any nuclear armed aggressor will make any real distinction between Scotland and the rest of the UK. Besides, nuclear weapons are not exactly known for their precision and the UK is a fairly small island; even a relatively small nuke in Cornwall would affect many north of the border.
Twon