Almost all changes—in fact, all of the changes—have been made without a referendum. The only referendum we've had was a U.K.-wide referendum on changing the system of voting for the U.K. parliament. As I said earlier, that was the AV referendum, changing to the initial vote system. That was not agreed by the electorate, so the change to the system did not take place.
Insofar as there have been changes, they've all been introduced without a referendum beforehand.