The UKIP is usually only successful in European Parliament elections where it takes a chunk of the most rabidly Eurosceptic Tory vote. Unless Euroscepticism becomes a campaign issue I don't see the UKIP becoming an effective spoiler against the Tories.

The BNP is a different beast, polling consistently across elections.

I'd say there's also a class-based distinction with the BNP appealing to a "lower" class than the UKIP. The latter is more nationalistic and less openly racist.

The brainless should not be in banking -- Willem Buiter