It's going to be interesting to see how this will pan out. Westminster set the precedent for holding a referendum when the Edinburgh Agreement was signed, so it'll be fun watching them get tied in knots trying to say no this time. Could the UN say no, given the right to self determination is in their charter? The rumblings from the EU seem to be broadly supportive but I'd guess they'd adopt the same "not interfering" card. Bet there's talk behind the scenes though.
As long as the poll results continue to rise, Westminster will find it increasingly more difficult to refuse a second referendum. They do seem jittery at the moment so probably not long before the media campaign against independence kicks off.