A little bit of background - probably the majority of UK politicians believe the EU is a good thing in the final analysis, but a large chunk of the Tory party is fanatically opposed to it, and would happily burn the party to the ground if they thought it would get us out. Those people aren't as crazy as I just made them sound, but like all fanatics they're not particularly good at converting moderates to their cause, making our European debate somewhat dysfunctional. From abroad, that probably makes us look like crazy people that make impossible demands one year then come back cap in hand the next.
As Hamerstein says, David Cameron has promised an EU referendum, although personally I suspect that's a local political ploy. Britain will probably have another coalition government after the next election, but the Tory party needs some time out of government to tear itself apart over Europe (as they do once a decade). By promising a referendum the other parties would have trouble supporting, he can politely rule himself out of a future coalition while making himself look credible going into their next civil war.
For what it's worth, my current opinion is that in principle Britain belongs in a monetary union but not a social one, and since our politicians have shown no interest in giving us a balanced argument, I generally look to
Turkey's bid to join the EU as the only meaningful data point about the sort of EU we're actually getting.