If we are going to spend so much time talking about the possibility of a hung parliament, it is worth noting that you don’t actually need 324 MPs to have a majority in the Commons. As John Rentoul reminds us, Sinn Fein MPs do not take their seats as they refuse to recognise the legitimacy of the Westminster parliament. (Although, in one of the many concessions to Sinn Fein that turn the stomach they are still allowed to have offices in the Commons and claim a salary and expenses) There are currently 5 Sinn Fein MPs and the polls in Northern Ireland indicate that they might well pick up some more seats. So, the Tories could well be a few seats short of a Commons majority in theory but have one in practice.
Obviously, if the Tories were in this position governing for them would be a very hard slog. No Cabinet Minister would be able to take a foreign trip with any confidence that he wouldn’t have to suddenly rush back for a vote and the party could not afford to lose even a handful of MPs on any vote.