Bulkhead to dashboard wiring connector

[306Puggy]

Right I've got my dashboard off to do the heater matrix but there is one thing that is stopping me which is the main wiring connector which goes to the dashboard. I cannot for the life of me figure how it comes off. I've taken the allen bolt out and have ended up breaking the plastic over the top but I can't get it off. Haynes just says to disconnect it but doesn't say how. Here's a picture of what I'm talking about:

I've had a look through the gti guides and they don't mention it being a problem.