ocker = yobbish. - I really don't think that that captures the subtlety of the word; its really more unconsciously yobbish - a bit like hillbilly, if you like. I think yobbish has more pejorative and consciously uncouth connotations.
Also, the glossary of Oz expressions to which Tsuwm linked has to be viewed a little circumspectly - as with all guides to "argot", it's probably out of date as soon as it's written. A fair few of the expressions are also very ocker themselves!!!