I wouldn't actually be that unhappy with a lib-tory coalition.
The policies that I most disagree with from the Tories would undoubtedly be chucked out by the lib dems. I'd rather see a Lib-lab coalition but anything is better than Tory majority.
But with the Tories still refusing electoral reform, I can't see how the lib dems could support them.
It's the Lib dem's golden opportunity for some form of PR/AV and their MPs would never allow them to throw that chance away - surely?