I think the UK is well within it's rights and should take a hard line with the SNP and the independence campaign.
In the possible event of Scottish independence then the rest of the UK should shut Scotland out in the cold. Scotland will have absolutely no rights to any free rides from the RUK.
Border checks. Stringent ones.
No currency union. Invent your own money.
No cooperation and agreement on sharing anything. Your independent, this is the reality.
Every asset of the UK than can be moved from Scotland should be moved.
It should push hard to ensure Scotland should have to start from as close to scratch as possible.
Use it's influence to ensure Scotland must re-apply to international organizations and such from the beginning. Full EU accession process. The works. If Scotland wants to go it alone it has to earn it like every other country.
Scotland should ideally be kept outside of NATO if the RUK can manage it.
No duel citizenship so that people who chose Scottish passports lose their UK ones.
It should also encourage as much business and talent to move from Scotland to the RUK, to boost the already inevitable tide of people and capital from the country southwards.
These suggestions aren't out of malice or spite but simple reality. If Scotland can't go it alone and survive entirely on it's own two feet then it doesn't deserve independence does it? The SNP's attempts to get independence knowing full well Scotland can't cope and prosper that way is treason, not to the queen or the UK, but to the people of Scotland.