Right, I think I've got what the "Cod-Left" is now. As far as I can tell, the Cod Left are left wingers who aren't working class enough. I think it probably all started around the time of Oasis and Pulp when it was no longer a stigma to be considered working class and people all of a sudden decided it was now cool. So prior to that, while working class people were striving to invent a new class - lower middle class - because being working class wasn't cool, especially for people who were doing ok with their lives considering where they came from, now everyone wants to be working class. If you need any more info on that go listen to Pulp's 'Common People'. That really does sum up nicely what I mean.
If your left wing, and fighting for the working class against the middle class, then you probably don't like the middle classes too much. But seeing that, proportionally, the middle classes are far more interested in politics than the working classes, it's quite likely that the left contain a high proportion of middle class people (probably all of them are in fact). This means that it's quite cool to be left wing AND working class, and also quite unique.
So, the Cod Left...
It's a bunch of middle class oinks (ie 'the Left') arguing over who's the most working class