It's going to be difficult, but not impossible. The difficulties lie in the fact that it's a hidden process, both emotionally, physically and legally.
What I mean by that is - you can't tell if a woman has undergone this process, simply by looking at her. When I was growing up in London in the 70s, I was aware of many older Africans who had tribal scarring on their faces. This is something that appears to have completely died out now, because you don't see anyone of African descent with these facial markings. I assume that second and third generation Britons of African descent have simply moved away from this custom.
However, FGM isn't obvious. And even if Islington is able to crack down on the practice here, what's to stop parents from taking their daughters abroad for the 'procedure'?
I think a combination of education, and 'Anglicising' (not sure if that's a real word) will have a positive impact on reducing FGM, but within a generation is pushing it.