Er...your link is for local elections. Not General. Local elections are notorious for protest votes. More so than the Euros for which you used the same excuse earlier.
Maybe you need to check your own links more thoroughly.
Here's one for General Elections for Dagenham.
http://en.wikipedia.org/wiki/Dagenham_(UK_Parliament_constituency)#Elections_in_the_2000s
And here's the result for when John Tyndall (middle-class) first stood there for the BNP in 1994.
Notes
BNP gain 7% of the vote.
Lab gain a positive swing of 19%
Tories have a swing against them of 26%
BNP votes from Labour you say? These were their original Dagenham 'base'. Tory voters.