Polls are often wrong, but they're not generally
that wrong. I think the most likely outcomes are either: the Tories hanging on by their fingernails with a majority so tiny they have trouble pushing through much of their further programme of cuts and privatizations - this should be helped by large numbers of non-hard-left Labour MPs warming to Corbyn due to his performance as a campaigner over the last few weeks, and Labour as a whole actually starting to act like an opposition party at long last; or a hung parliament, with everyone other than the Tories cursing Corbyn for having ruled out an alliance with the SNP that would've given the two parties a comfortable majority between them. Even if Corbyn were to change his tune - or be replaced as leader by someone more amenable to an alliance (
although not Cooper, apparently) - Sturgeon might well feel too snubbed already to consider it, and instead opt to let England go hang under the Tory lash while banking on Scottish independence a few years down the line, and an immediate application to join the EU.
Of course, I understand the appeal of setting your expectations as low as possible before something like this...