lets be fair now. the Liberals got their vote on PR early on, and they lost (badly). there was no requirement for Tories to support it. the quid pro quo for that policy was 5 year fix parliments and constituency reforms.
Lords reforms is another seperate policy area, one that Tories support in principle (its in the manifesto to do somthing) but not the proposal offered, in particular the lack of detail on the mechanics of how the new Lords would work in concert with the Commons.
rather than address problems and rework the proposal Clegg adopted a take it or leave it approach assuming Cameron would bring the party in line. poor Cleggy, for the leader of a fractious party doesnt understand the Tories are also a fractious party (arent they all). now he's playing to the home crowd for the conference season proposing a wealth tax, no doubt to arbitarily penalise some tiny group of the population that wont bring in any meaningfull amount of money, yet consume political capital.
It wasn't PR it was Alternative Vote, and entirely different kettle of fish!