They've gone past the point of no return now. SNP having 56 seats means bugger all in Westminster - and with English votes for English laws looking more than likely - SNP need to get Scotland the hell out of the UK. Staying where they are means they are in the palm of the Tory party. Vote SNP, get Tory. Biggest act of a region cutting off it's nose to spite it's face that I have ever seen.
They only got 50% of the vote though and 45% in the referendum. Douglas Hurd was right earlier on the BBC, there needs to be a new Unionist party in Scotland, separate from the Conservatives/Labour/Lib Dems.
You could look at it another way. Vote SNP & get a decent socialist party, that has more in common with the UK Green party. Well done SNP. They aren't going for independence, but rightly want fully devolved power. You cannot argue with their mandate. A 20 year old student ousted Labour's tactician.
You spend your juvenile years buying his albums and spending your last new pence British Railing it down south to see him in concert. You suffer year after year thereafter, listening to more albums with less and less enthusiasm, cherishing the odd nugget, sticking up for him when he suddenly rises from the grave, even though his recent effort isn't really that good. Then he goes and spoils it all, by saying "Scotland, stay with us". Ex-pat. Bowie.