What would I do?
Well, personally, I'd legislate a referendum on the EU for October. UK wide but excluding Scotland if they vote YES.
Why would I do this?
Well if you've been watching the polls as I have, you would notice that when Barosso stated that Scotland would have to exit the EU if they exited the United Kingdom, the polls jumped 6% in favour of a Yes vote.
6%!
That is 6% of votes which can be bought. The Yes campaign would never recover from it. They can't overcome a 6% swing at the last minute.
Also, for these Scots, "Better Together" sounds much better as "Better Together out of the EU". They're willing to go it alone if they have to but would rather be out of the EU as part of the UK than in it as part of the UK. If the only choice for them is to exit the UK first and then deal with Salmond after when he goes after the EU, they can deal with that. All they need to do is vote UKIP in the first true "Scottish National" elections, ever.