I disagree, dj. For a start, if UKIP had some MPs had some MPs, they might stop their constant whinging about being the anti-establishment underdog. Secondly, it would give them a voice and people would be able to hear what charlatans they are. Thirdly, they would be put on the spot and expected to come up with solutions rather than constant negative sneering. Fourthly, they don't have enough people with the calibre to be MPs, although some Conservatives might join them. There's nothing like giving people a position of responsibility and seeing how they would do things better.
PR would also have the advantage of allowing more Greens to be MPs.