I've never heard of UKIP before. Steyn is so wonderfully informed on multiple countries.
UKIP got a big vote in the last European elections with lots of protest votes but are widely seen as a one issue party and so not really a factor on the national level.
It's an oversimplified analysis to say that UKIP cost the Conservatives x number of seats. People who vote UKIP are by definition rejecting the Conservative policy on Europe to such an extent that they would rather register a protest vote for a candidate with no chance of winning and risk allowing a more left-wing candidate in than vote Tory. It's a stretch to imagine that all of those people vote Tory if UKIP isn't there.