I can't imagine the polling accurately reflects public sentiment.
There are probably a lot of unionists who don't want to be seen in the same camp as Cameron, Clegg and Miliband.
I think this is different to Quebec, because if I remember correctly, there was a higher voting age in Quebec. 16 year olds can vote for Scottish Independence, and Salmond intends to fill the booths with young unemployed Scots who want wealth redistribution and watched too much Braveheart.