How does this fitting disconnect please?I can't seem to get the dark grey section to rotate independently of the lighter section which is what I'd expect. Can I just pry up on the clips at side?

Collar was just a bit stiff. Rotated a bit then a tug disconnected.

Careful not to lose the grey bit! I did that and had to tape it up with duct tape, until I got a new one ordered from main dealer. It was quite cheap though.