"More likely is a reform involving the Alternative Vote. That could come about even if the Tories formed a minority government, since in a hung parliament there would be a majority likely to support that, who could outvote the Tories and set up a referendum to bring it in."

I don't think that would really happen. The vast majority of bills are generally introduced by government ministers and in a Tory minority administration (bar possibly an Ulster Unionist) all the ministers would be Tories. The Tories point blank refuse electoral reform. Opposition members have an opportunity to propose Private Members Bills but in reality in the past only uncontroversial legislation ever proceeds to bill stage - though it can cause a caffufle right enough so can directly effect govt thinking. The problem for the opposition is that Labour propose the Alternative Vote system in their manifesto whereas the Lib Dems totally disagree and support the Single Transferable Vote system. So if a Lib Dem backbencher managed to introduce a private members bill it is unlikely they would get full Labour backing and vice-versa. I think the only way it would come about in the next session (unless there is a complete Tory u-turn) is if we have a Labour-Lib Dem coalition where the method of voting to be proposed is hammered out and agreed on right at the start of party negotiations. A Labour leader may be much more co-operative with the Lib Dems if the keys to No 10 are on offer - whereas as members of the opposition they might be far less liekly to vote for Xmas