I am not sure that it is unreasonable to have a referendum on such an important issue every ten years. I wish that we had one about EU membership every ten years. I bet that we wouldn't be in it now.
Surely you aren't suggesting that the EU collaborators would only call for referenda in order to push their country INTO phpbb_the EU and not once they are in?
Even though there wil be a referendum on the EU Constitution, perhaps UKIP ought to really push the next general election as a genuine opportunity for the public to vote on EU membership. The emphasis is important, and will define how people see us in the election. If we are just another party that happens to want out of the EU, I don't think that we will do so well. If we create an "us or any of the others" choice for the electorate, then we could do well.
We need to define the terms of the election, rather than letting the others get away with arguments about crime and health and so on. Bush kept the presidential election about foreign policy and security, which is why he won the election. We need to keep the discussion on the EU.