^^
IF the SNP win their 40 seats and end up supporting a minority government, we get the situation where a group of MPs, who we didn't have any chance of voting for, and whose whole raison d'etre is the break up of the nation, holding the rest of us to ransom.
Nope...think it through.
If NS gets into to some sort of coalition (even a loose one) she will be faced with compromising the very politics which are proving so popular in Scotland, or pulling the rug from under Milibrand in short order, which will simply lead to another general election.
The danger to the UK from a SNP/Labour coalition is emphatically not constitutional change or a massive shift in the main political landscape. The danger is economic & political uncertainty & stasis for an indeterminate period.
If the jocks still want independence (and many want it more than ever) their best hope is a continuation of the current coalition, which will polarise and harden feelings on both sides of the border. (as evidenced by Cameron's latest pledge: English laws for English voters.)