I might take a photo later. The knob does screw off, but the shaft is way bigger than the hole in the top of the rubber boot. The shifter comes out of the gearbox by removing a sirclip.
Geoff - If I got a boot that would side over the shaft, the oil would still be able to get out the top. Unless I cable tied it to the shaft. (But that's just dodgey, yes, I know thats what you would do.)
Duncan - I think this wed might be an SAU meet. Snowman? correct me please?