UKIP are centre-left, not 'extreme right'. On economic issues, they're to the left of the big 'left' party in the UK (Labour, who are really a more centrist party) and only really go to the right on immigration rather than social issues in general. You're confusing them with the BNP.
On the economy UKIP are certainly right wing. They supported a flat tax for gods sake. More broadly their entire reason for existing is to promote deregulation of all kinds (financial, environmental, health and safety etc).
I wouldn't call them centre-left, they're a bit of grab-bag of policies e.g. some member have been a bit libertarian (which can be socially "left" but economically "right" depending on particular issues). But Xenophobia is the biggest theme, see for yourself:
They're scoring pretty well on the class right-wing themes of "more police", "putting bad people in prison for a long time prevents crime", "down with environmental policies", "make sure these brown people pay taxes but don't get benefits". I'm liberally translating the program, in the spirit of their "No to Political Correctness - it stifles free speech" bullet point.
Of course "Teach children positive messages and pride in their country" (which immediately brought to mind a law passed by the right-wing in France aiming at emphasizing "the positive role of colonization").
Is wanting to leave the EU xenophobic? The EU is currently failing. Or wanting immigrants to be have sufficient points and be able to support themselves? This is standard for many countries.
