I'm stuck in room 16893.  I have saved and explored both left and right on the upper and lower level but the only 2 things that I can think is that I've missed a pink key to go right down on right (but have been back and explored all the level above and I'm sure I haven't and cannot get to the pink key in this room because of a rock fall (or whatever it's meant to be) so all I'm left with is opening the grey door but I cannot find the trigger and I've even been back up and tried to repull every lever. 

Could somebody please give me a hint>

Hi Skally. You can get to the pink key from the top level. Just jump onto the chain.

I've tried that but I'll keep trying until I get it!

Thanks

You might have to "fall" onto it instead of jumping. Just let Jack drop and hold the left arrow key down so he lands on the chain. Good luck!