Probably due to UKIP offering a sane nationalist alternative: while most of UKIP’s vote (interestingly larger than the SNP’s vote, but only winning one constituency) doubtless came from the Tories and Labour (their protectionist stance vis-a-vis British jobs in the matter of immigration doubtless drew some Labour supporters), I have a feeling pretty much everyone who might ever have voted BNP as a protest vote went UKIP instead, leaving only the very small hard-cord BNP types.
Wrong. The Conservative Tories did extremely well. They took votes away from all the others...except the Scottish Nationalists who took votes away from Labour but not the Tories. No overlap between the Scot true loonies and the Tories.
We need a sober sane UKIP type party in this country.