I currently work in local governament, although not one with BNP Councillors in it.
Word is that these BNP councillors are simply ineffective in the real political world of the Council chamber. They don't turn up much, and when they do they don't say much (if anything). One theory is that they are simply waiting to get accustommend to the political world, another is that they really don't know what they're doing once they gain any sort of power.
However, the message is simple. On local issues these people really aren't being effective at representing local peoples views. You need to do more than just get elected!
The rise of the BNP does cause some concern for those working in local government. Who wants to work with closet nazi's? However, if they are elected, then the conclusion is the voters want them there. So Council Officers have to work with them. An uncomfortable situation to be in, and I feel for those officers involved in such scenarios.