The thing exercising my mind is the dismal performance of the party within the UK since 1994 and under Farage’s stewardship
There has been a sea change on two fronts since the 90s. In that decade, and the first few years of the 2000s, most people were unconcerned about the EU. They were doing all right and the EU seemed a largely benign organisation (to them, that is). Of course, when the European elections came round and those who were suitably motivated to vote began to consider their options, there appeared one party that wanted less intrusion from Brussels and they duly voted. That is how Nigel Farage got his seat and that is also, and why don't people mention this? - how Danial Hannan got elected. He is a Tory, but highly eurosceptic. Why doesn't he get the flak?
Since the financial crisis, the bailouts and the increased moves to an EU superstate have finally brought the ogre of the EU to the attention of the masses (well, some of them anyway). Hence the rise in UKIP's fortunes.
At the same time, and this is my second point, the coalition has - to many ardent Conservatives - been a disaster. More government, not less as promised. More sleaze, not less as promised. More erosion of our sovereignty, not less as promised. There is a feeling that there is nothing to choose between LibLabCon. Where do those votes go? To UKIP.
Thus to summarise, the fact that UKIP have no Westminster representation merely reflects the earlier, and now outdated, view of the electorate that Europe doesn't matter; that a Conservative-led coalition would be a massive antidote to the Blair/Brown years. By waiting in the wings as MEPs, the leadership has been quietly building a viable alternative to the stifling tripartite political system we have been forced to endure. UKIP is massively underfunded, but it has kept going and will reap the rewards of its work, I am sure.