The thing about Nick Griffin is that a lot of what he says (in public, to a general audience) does make sense. He is far from stupid, he went to Cambridge Uni after all. Beneath the intelligent arguments, though, lies a nasty little racist.
His arguments about a disenfranchised white working class do have some merit. When I was a child, cleaning ladies were working class english (mostly white, some caribbean), as were waiters, labourers etc. These jobs commanded reasonable money and allowed these people a sense of pride and contributing to society. These jobs are now done by immigrants, sometimes on the minimum wage and more frequently illegally employed on far smaller wages. The effect of this has to keep inflation down and allow the middle (and dwindling upper) classes cheap servants and (relatively) cheap restaurant meals. The other corollary, however, has been a disenfranchised white working class, on benefit, with no incentive to come off it (as jobs they are capable of pay so little).
Immigration is a wonderful thing but it cannot be uncontrolled either in terms of speed or composition. A society with no immigration is like Japan, rapidly ageing and without the zeal and drive of new immigrants trying to build a new life. On the other hand, completely uncontrolled immigration (coupled with benefits skewed by positive discrimination) is a disaster for a cohesive society. The vast majority of Anglo Saxon countries (U.S, Canada, Australia) have strict controls on immigration. With English as the global language, this is necessary.
Until the mainstream parties address the above issues and we all consider the cost of our "wonderful" Russian/Polish/Filipino cleaning woman who is paid marginally above the minimum wage in cash, there will be a place for nasty racist far right parties.