It's interesting that so many people refuse to even contemplate the possibility that the two parties might have some similarities, when the BNP clearly *do* feel that UKIP is their successor. In Mikey's link above, their spokesman clearly states that UKIP is the party that has taken on their message, and even their former leader has come out and said he will vote UKIP come the election.
I realise there are plenty of ordinary people who support UKIP - and this really isn't intended as a dig at your average UKIP voter, or intended as an implication that they are racist. But the party has done NOTHING at all, despite frequent assurances that it will, to stem the tide of these undesirable influences in the party - it has even put such people forward as candidates for public office.
If you care about UKIP succeeding, this should concern you. If you are a potential voter, you have influence that UKIP currently needs desperately. Use it.