The current conservative line on our EU membership is that we must insist on repatriation of (some) soverign powers, and if we cannot get them back then we must leave the EU.
For this to be a rational proposition there are three models of the UK to be considered.
1) The UK 'as is' as a member of the EU
2) The UK independent and not a member of the EU
3) The UK as a member of the EU with some repatriated soverign powers.
Cameron and the conservatives are conceding that 1 is the worst possible option. That the UK being independent would be better for us than our current situation within the EU - exactly what UKIP have been saying for over a decade now.
Having ruled out scenario 1, there may be discussion on the merits/differences between scenarios 2 and 3.
For 2 and 3 to be assessed against one another, both options must be fully examined and modelled - this is a dream come true for UKIP - scenario 2 must fully analyse how an independent UK would operate outside the EU, expensive analysis that UKIP couldn't dream of funding itself, but work that the government must now pick up.
Let debate commence!