Thanks for the advice.
I've managed to disconnect about half, but it doesnt give access to the lamp, which must be somewhere inside the threaded black plastic tubing...
I've tried twisting and jiggling but i'm not getting any play at all, and everytime i feel the plastic start to buckle i figure i'm trying too hard. I can undo the nut around the plastic, but it only seems to loosen the button itself.
I've attached a photo in case that helps. Have you guys come across this particular type of button before?