Alex Salmond wants to drag out the movement to Scottish independence as long as possible, always moving towards it, never reaching it. Because if he reaches it, then his job is done, and his role is obsolete. Conversely Cameron won't lose much if he loses Scotland - the Scottish electorate aren't ever going to vote for his government anyway, so as far as he is concerned they might as well flake off. So it's not surprising to see Cameron pushing for an early referendum, which would trigger complete breakup of the UK, and Salmond manoeuvring to reframe the referendum so it does not mandate full independence.
Michael Moore, the Scottish secretary, confirmed that the UK government's legal advice was that the Scottish parliament currently had no legal authority to stage the referendum in any form... And, in a deliberate move to prevent Salmond staging a multi-option referendum, Moore said the UK government would temporarily give Holyrood the legal authority to stage that referendum but only if it was a single "yes" or "no" question about independence, and only if the referendum was run by the UK Electoral Commission.
FWIW I would hate to see the breakup of the UK. I think the workers are stronger united, and the people of Scotland would be better off joining their forces with the rest of us to restore the country. But I guess it's their business in the end.