They have a right to march under British law, so there's not really a lot we can do about it.
The Police, rather than banning the march, should be looking to have enough of a presence on the ground to ensure the safety of the marchers.
If necessary, the cost of this should be passed on to the organisers, who in this case are Islam4UK.
I don't support any group that claims to be a platform for extremists, whatever their religion, but I do support their right to protest.
I'm ex-forces (or ex-paid oppressor as my brother's father in law insists on calling me) and, if I'm honest, I didn't really care what people back home in the UK said or thought when I was out in the Gulf in '91. Having said that, it was a lot less dangerous then!