I am not suggesting you do this BUT I had to grab the twist and turn thingy with a pair of water pump pliers to undo the sodding things. There wasn't enough room to get proper leverage on it otherwise, from what I remember.
Best thing to do is find one that does undo easily to check which way it undoes, and then try the tough one GENTLY with the pliers or similar.
There is a way to get the whole light fitting out I think too, but I'd have to check on another forum to get the instructions! Can do that if you want.