You could convert to full PR without a referendum, using the precedent of the Euro elections, and the fact that unlike AV, it doesn't require the voters to do anything different at the ballot box, in terms of the fact that they will only place one cross, just for list candidates unless you have top-up. Clegg should have insisted on this as a pre-requisite for the coalition, which just goes to show what a crap leader he was (that he didn't).
Ian Speed ● 4189d