Whether a candidate finishes 3rd, 4th, 5th or lower is a red herring. I remember in the Hartlepool by-election where the Conservatives fell from 2nd to 4th behind UKIP, Labour attempted to pass this off as Michael Howard's leadership in meltdown. The Conservatives went on to catch up a reasonable amount of ground in the General Election.

The fast that the BNP managed to get 3% of the vote in a FPTP constituency is worrying irrespective of what position that turns out to be, but the cause is pretty obvious: with none of the main three parties making any convincing offers for the least well-off in society, it's not surprising that the BNP can fob some people off with their image of being champions of the underdogs (as long as the underdogs aren't black, gay, Arab, Jewish, or Eastern European).