we don't have chavs. we have neds 
it is all of those things but chiefly a complete disregard for societal norms of behaviour. they are like modern-day outlaws
I was in a sports shop the other day and two neds came in. I was queuing quietly to buy socks and had been gazing at a pogo stick near the till. Of course one of the neds immediately leapt on it and started boinging around the shop, knocking boxes flying and causing general mayhem.
I'll wager that he was doing what deep down I and the other people in the queue would probably have wanted to do, were we not tied down by normal standards of protocol. In short, he didn't care what anyone thought, he did what he wanted. Part of me wishes that was me. Most of me doesn't though.