Talking of the toilet system, seem to remember it was a funny arangement where each toilet flush motor flushed in turn and presurised the line, then the relevant flush valve opened to the toilet being used. The term 'blue rinse' springs to mind when working on a toilet and someone flushes any of the others in the complex....just try getting out of a cubicle in a hurry....!
the hydraulic bay was a great idea, ie putting a lot of the HYD components in there, shame they then put a hot APU air duct through it.
Lower galley...great for staff travel (not officialy of course) far more fun down there during the flight, helping the girls etc....