The head of No is proposing another referendum over the terms of exit in the event of them winning the referendum:
http://blogs.spectator.co.uk/coffeeh...o-referendums/
The idea being that it would prevent the No vote being a risk as you'll always be able to vote again in a few months whereas Yes would be final. Another way of looking at it is that they don't have the power not the obligation to actually hold another referendum and may take that No vote as final.
Plus it's bloody stupid and just prolongs the amount of time spent dealing with this issue. Like the Scottish Referendum we should make a decision then get on with it. We can't spend the years obsessing over Europe.