You will need to watch some of the footy violence films if you're gonna do a British gang project.
A point to make out as well is that gun crime isn't that high in the UK anymore, knives and blunt implements are used to a considerable extent these days.
So perhaps you could have gangs of 20 or so people (which is usually the case) with one shotgun or rifle a few air-rifle pellet guns and small arms.
Very interesting project, I want to do the same sort of thing, but I am planning on using the rules (which the name of has escaped my mind) that were released earlier this year.
Oh yeah, no go zone!

I'm liking the start. But yeah, definately watch some British footy violence. My uncle was an extra in green street.

4th one is best, the others don't resemble the UK in any way, shape, or form.