After 2 day's under my car and having to drop the gearbox to gain access to the clutch mechanism, I finally found out what caused the clutch pedal to hit the floor and stay there as I was changing from 5th to 6th the other day:
The right hand clutch plate had completely come away from the left hand plate carrier!
Holy crap, is your flywheel ok? What engine is it? I have a golf and will need to do the clutch early next year and i know some Audi and VW have the same engine.