For what it’s worth, the LibDems would be mad to go with either the Conservatives or Labour. Neither of them would do any favours for the LibDems – and if they think that either of them would permit any form of proportional representation – and, thereby, lose the chances they have for staying in power, they are really stupid.
Sooner or later, the UK will wake up to the fact that the current system disenfranchises so many voters and it will change. But not yet.
What the LibDems should do is try to educate the voters so that they get enough votes which are translated into real seats to be able to push through PR. And hope that the voters aren’t scared by the other two parties, like they usually are. Only then will the change happen.
There. My opinion. For what it’s worth.