Hate to point it out but by voting in you are voting to be in under Dave's opt outs - so no further political integration for the UK while the other members work towards it for the other 27. You can't actually vote for as it is now - i.e. no change.
This is nothing new. There is a policy within the EU treaties to move towards ever greater political and fiscal union. Something that allegedly CMD has managed to get an 'opt out' for the UK.
Something the inners can't answer ( and never attempt to answer ) is how the other 27 members can head...