It's all about voting systems.
Electoral reform was the key to the LibDems coming to agreement with the Conservatives, and now they've agreed to have a referendum on the Alternative Vote voting system.
Well, PR was the LibDem's dream (and there are plenty of people still campaigning, with LibDem support, for such a change). But, being realistic for the moment, the two main parties were never likely to support it: like turkeys voting for Christmas. In the end the LibDem coalition choice boiled down to a deal with the Conservatives, where they sacrifice a few of their policies for the sake of stability and a historic chance of power. Or do a deal with Labour that offered what they wanted, but at the price of stability (how long would such a ragged collection of parties lasted? weeks? months?), as well as having questionable legitimacy.
PR is, it goes without saying, the fairest of them all. But, I find it hard to believe that most British people would be able to stomach a PR voting system that would almost certainly result in coalition governments most of the time (perhaps as much as 90% of the time, barring huge landslide victories). Let's not forget that political reform was a gradual process over many decades in the 19th century.
AV is the closest to the present system, that offers a kind tweaking of the system. By counting up second preferences in constituencies, it allows more of a chance for other parties (the British like the idea of fair play) to win seats. I saw a breakdown of this on the internet, using the 2010 election results: under AV, the Conservatives and Labour would have had more-or-less equal seats, although less than now, and the LibDems a few more than they had before the election. The benefits of this system over PR is that, while it certainly makes hung parliaments more likely than now, it still offers the "stability" which a lot of British people seem to prefer.
Of course, this attitude might change very quickly. In which case, the UK will join the rest of Europe in having a PR system that everyone seems to think works fine for them. It depends on the country. One thing's for certain: coalitions force politicians to stop acting like children and behave like real adults.
To negotiate and compromise is a sign of maturity, not weakness.