I agree with Saqib. All four boys have the type of accents that could originate from anywhere in the south of England, especially the southeast. It would be hard to pinpoint a particular city or region that they come from. The other noticeable thing is that the two boys who are sitting down in the second scene (the one with the white T-shirt and the one with the blond hair) have more of a 'lower class' Estuary accent than the other two. The other two boys have slightly more middle-class accents which are closer to standard relaxed RP.
Cockney is restricted to older people in certain areas of East London, and actually is becoming increasingly rare. In fact, it's predicted that it will have disappeared fifty years from now. Young Londoners from the traditional Cockney areas now speak very differently from their parents. Among the younger generation of working-class Londoners, the dominant accent is MLE (Multicultural London English), which reflects the Asian and Afro-Caribbean influences in the capital.