1) UKIP aren't "far right". Yes, they have members and supporters who are or have been members of far-right groupings, but so do the Tories. Policy-wise, Nigelo Farago (who controls the policy process, not some two-bob councillor who used to be BNP) hasn't put out anything to the right of 1970s Conservatism.
2) UKIP may well have "the popular support 5 million people", although I'd disagree with that figure, and say that while UKIP's ambitions are for such support, their projections are based on best-case scenarios that are currently pie-in-the-sky, and depend on the meltdown of the three mainstream parties.
3) While it's entirely possible that UKIP's standard will advance at the GE (maybe turning their two seats into a handful), their support is too geographically-diffuse for even the purported 5 million to mean that they'll achieve more than that this time round.