I feel a little sorry for dave here.
He was bumped into having a referendum, by the prospect of UKIP snapping at his heels. Of course, this in the end, turned out to be no threat at all. In fact, at the Election, the Tories won back back one of the two seats that they lost to UKIP the previous year, so no great harm done after all.
But he now faces a much worse prospect...his own Tory militant tendency. They put paid to a previous Tory PM, who left Downing Street with a whole back-load of knives sticking out of him, and they could do for dave as well, unless he is very careful.
None of the main political Parties want out of Europe, and he most certainly doesn't himself. So he is hedging his bets as much as possible, and who can blame him. He only has 3-4 years left at Number Ten and he wants to decide himself when he leaves, not be pushed by the swivel-eyed loons, and the bar-stewards.