The right of an organisation like the BNP or Islam4UK to stage a march is not the same thing as their right to free expression, but it's pretty close. The right to free expression demands that everyone can say what they think, or even just what they want to say even if they don't really believe it, somewhere, in a publicly accessible way.
But does that mean Protestant Ulstermen should be able to march through Catholic areas, taunting them, celebrating the defeat of the Catholic cause in old battles? Or that a small group of Islamists should be able to stage a provocation in the town, Wooton Basset, that has become synonymous with the return of the corpses of British servicemen and women to the UK? After all, both Orangemen and Islamists can express their views freely, in public, in other ways, so a ban on either would have no effect on their right to free speech (so I disagree in this particular with Longrider).
In both cases, though, there are political issues. As Steve says of this latter case:
In all probability, Choudary is hoping that his march will be banned. That way he can claim that the British authorities are so scared of his jihadi army that they abandon their principles. Free speech, he will claim, doesn't apply to Muslims. By allowing his march to go ahead his bluff would be called. His pathetically small group of wannabe-theocrats, marching through the cold streets in their night-dresses, would look more ridiculous than frightening.That's absolutely right, and this, not the right to free speech, is the reason the march should not be banned. However, I can think of an interesting precedent, from the late 1970s.
James Anderson was Chief Constable of Devon and Cornwall (it may have been Andersen, I can find absolutely no reference to him on the internet, despite the fact that he was one of the best police officers this country has ever had). He is not to be confused with the bearded religious maniac James Anderton, who was Chief Constable of Greater Manchester at the same time.
At that time, the National Front were staging marches in British cities and towns, and the Anti-Nazi League and others staged counter demonstrations. When the NF decided to march in a town in his jurisdiction, Anderson simply hid all his police officers. They were there, in vans, with anti-riot gear, but they were hidden, nowhere to be seen when the NF arrived at the railway station. So, rather than march unprotected, the National Front went home.