The only way PR could come would be if the Lid Dems held the balance between Labour and the Tories, dug their heels in, and got one of those parties to offer it in exchange for support.

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.

And quite conceivably the Tories could offer this in exchange for L9b Dem support. After all they could still campaign for a No vote in such a referendum.