"Chav" is slang for a low-class British person, usually young and poorly educated: the type who stand around on corners and might even be petty criminals (public drinking, fighting, cursing, maybe grafitti, etc.). So "Chavs talk" would be the kind of accent and slang this group uses.

嗯，我知道了，我只是想问下所谓的chav talk是接近标准的英式发音，还是很差劲的发音方式

我不是英国人，但我听说chav是贬义词，我建议你不要称呼别人chav。