The problem is, people view BNP as an entirely racist nazi style party and thus don't "want" to vote for them out of fear of being labeled the same.
When you read the manefesto, a lot of policies make sense and would do a lot of good, not all of them, but most of them.
Unfortunately, as I see it, the BNP would be one of the only parties who would come in and make the changes needed "promptly". Lib dem, conservative will come in and ride the "it was labors fault" train without actually doing anything untill the economy gets somewhat sorted out.
The be all and end all is, no single party will reform the system, but in my opinion it will take a "radical" party in power (even for just one term) to get the cogs moving.