The butterflies which came out of the decision not to give a referendum would be interesting. Would Labour decide to step in and fill the void by offering a referendum themselves? My gut would say probably not, but if they did maybe and we saw more defections to UKIP the two would take more votes off of the Tories in 2015, and Miliband would be in the 250 seats plus territory that might mean Labour could realistically form a minority with the SNP, so although the Tories would still win the most seats by some way, they would be in minority, and the result would be altogether messier, and maybe there would be a second election.
If neither of those things happen, the result would probably as other posters have said, a few seats would shift one way or another but nothing major. The Tories would form a minority government, the Lib Dems would probably not consider joining them again after losing most of there seats.