Alternate Voting is not a method of proportional representation. It is another voting scheme. The Liberal Democrats wanted a vote for Proportional Representation and the Conservatives agreed to a referendum, but on the rubbish AV scheme instead. Many many people voted against AV because it wasn't as good as PR and didn't want to change multiple times.
PR is superior to AV and FPTP and should be implemented. It shouldn't even have a referendum. It should just be done.
> Alternate Voting is not a method of proportional representation
Alternative Voting (AV) is a single member district voting system that produces results where the representations of policy views in the elected parliament are more proportional to the views in the electorate than first past the post, and thus is a method of enhancing the proportionality of the election system for a parliament when the status quo is FPTP.
It do so less than Single Transferrable Vote (STV) in multimember districts (AV -- known more often to US audiences as Instant Runoff Voting [IRV] -- is just the single-member-district case of STV, which supports any district size).
Its relationship to other PR schemes where not all candidates are directly elected by-name by general election voters (the most frequent being Party-List Proportional and Mixed-Member Proportional) is complicated -- those schemes optimize for proportionality of partisan composition of the legislature, but provide weaker accountability of individual politicians to the general electorate.
But PR itself isn't a system, its a (continuous valued, not even binary) feature of an electoral system. You can't "implement PR", you can adopt a system that increases (or decreases) the degree to which you have PR.
PR is superior to AV and FPTP and should be implemented. It shouldn't even have a referendum. It should just be done.