I've been working on some stats that might be of interest to OurKingdom. Using Guardian Datablog's release of election results I worked out exactly how many voters cast votes for candidates that weren't the winning candidates and how this broke down among the parties. It's not an often used measure of how terrible the voting system is, but I find it to paint a fairly vivid picture of the problems.
What I found was that:
67% of MPs are opposed by a majority of voters in their constituency.
53% of voters walked home away having received an MP they didn't vote for.
Conservative voters are the most likely to have an MP of their preferred party with only 32% cast for non-elected candidates, whilst 82% of Lib Dem votes were cast for candidates that failed to win election.
Unsurprisingly 'other' voters (for lack of time in separating them all out) went 94% to non-elected candidates but these also represented a smaller number of voters than voters for non-elected candidates of the three main parties.
I find the fact that a majority of voters remain without their representation of choice to be especially damning and I think it'd be fairly easy to make the case that as only a minority of votes ended up vested in candidates who will become MPs, there's a democratic legitimacy problem.
My data can be found in a more full form here.