It's because the deficit is coming down (albeit tragically slowly, because of the miniscule level of public sector spending cuts), increasing internal and international confidence in the UK. Cutting the unproductive public sector allows the more productive and more job generating private sector to thrive.
It's because even the pathetic welfare cuts the government are making are making work a more attractive alternative.
It's because of Britain's labour market flexibility (despite Labour's best efforts to stamp out any vestiges of it). Lower pay is never great, but they mean more people keep their jobs when things go bad, and companies create jobs much faster when the recovery takes effect.
It's because we're not in the Euro, and the pound has taken part of the burden of the recession.
It's because corporation tax and the top rate of tax has been cut, thereby attracting job creators and international companies.
Cameron and Osborne have not been nearly ambitious enough in their pruning of the dead weight of the state. The Tories should be far more savage towards the bloated mess left by Labour (together with the Labour shadow state of quangos, public bodies, "charities" who only work on "policy" funded by the taxpayer, etc). They need to be far more Thatcherite (and Lawsonite) in their approach.
But it's hilarious to watch the Guardianistas at MN falling over themselves to make try to discredit what is, however you spin it, pretty good news.