I am convinced that I first heard about the situations in Ceuta, Melilla and Lampedusa long before Gaddhafi got his scaffolding implant. The crowds we have known of, at Sangatte, for the last decade or two have come via that route.
The waves of refugees from Eritrea and Syria appear to be something new. Evidently, the instabilities in Egypt have left its borders somewhat leaky, too.
Personally, I think it's incorrect to blame Cameron and our intervention in Libya. It's like their is a tacit refusal to accept that Africa has had access to global media and the internet for years. They now realise what a **hole they are living in and, with Google streetview, exactly what Europe looks like, so they'd be fools to not be heading this way.
Nothing to do with Cameron, it is entirely due to global-scale inequality of standards of living. Give them a way to make their lives comfortable and they will stay in the land where they were born, if that's what you really want.