If they're anything like this [http://www.fat-pie.com/chavs.htm] then you are dealing with a chav. While I'm almost certain this entire thing is a satire, it does honestly encapsulate the stereotype - and frequent reality - of the chav lifestyle.
The 'hoodie' thing comes from chavs generally wearing sports hoodies all the time and doesn't, as such, refer to anybody and everybody who wears said item of clothing. It's a popular type of jacket / sweater so you're hardly going to be damned for it.
The main problem is most of the subculture originates out of low income areas where kids have nothing much else to do but to get together in large groups and lash out at the world around them, which comes from not having enough attention from parents, not being able to relate to others, whatever, handful of reasons.
I don't 'hate' chavs. I'm sure most of them have the potential to be decent people, but they unfortunately fall into social groups and routines that only exacerbate the problem until they're too far gone.
The stereotype, at least as far as I'd think of it, is fairly true to reality though the disturbance any given group of chavs can cause in a community varies from place to place. There are some 'chav' groups who dress and generally act like others only with less criminal activity and are pretty much 'normal' kids with a predisposition for promiscuity, underage drinking on street corners, certain fashion trends and tastes in various media.
At best they're just another clique. At worst they're a serious drain on valuable community resources.
Hope that helps.
