As to whether a unilaterally arranged Scottish Independence Referendum might lead to a meaningful NO result, there are countries in existence today where before independence the population did not have overt approval of the former "parent" country, or even seek it, for a referendum or other unilateral declaration which announced separation and total independence. This is a question similar to whether a person can leave and divorce a spouse - only a form of imprisonment will present an effective obstacle, not a promising tactic for maintaining unity. If any member of the UK club decides to end the thing then it inevitably ceases to exist in its present form and no posturing on legalities (sound or unsound) is going to prevent that. Whether other members would follow suit and leave is basically unknown, although some may say it is more likely than not. England on its own and outside the EU would undoubtedly be unable to maintain a posture of a great power (which once really was one) and, for perceived status, would become even more reliant on tagging onto the USA and partaking in their adventures.