Therefore, for the UK-wide government to be suggesting that they could offer the SNP a legally binding referendum, in return for it being held earlier** seems to me to be political meddling of the worst sort. The UK government hadn't offered a referendum, weren't going to hold a referenfum, and all of the UK-wide parties blocked a referendum being held when it was proposed during the previous Scottish parliament. Therefore, the only possible reason they can have for getting involved now is to prevent the mandate of the legally elected Scottish government from being carried out.
I don't know how I'm going to vote, come the referendum. But I do know that every time the UK government interferes it pushes more people to vote for independence from them, and that by playing political games like this they're playing directly into the hands of the SNP. They don't need to sell independence more than they currently have, they just need "The London Government" to alienate people.
*Whether they have a legal right is another matter - but that would be a matter for the courts to settle.
**The current polling indicates, depending on the exact question asked, that either it would be very close, or there would be a No vote.
Original post on Dreamwidth - there are comments there.