300 TDI Clutch problems

Morning all

My aunt has a 300tdi disco which has lost its clutch. The pedal goes to the floor and doesn't return. I have taken the gearbox off thinking it was the release arm fault but this appears to be fine with no hole. The master and slave cylinders have been changed and have made no difference.
My question is when the box is fitted to the engine the release arm still has 20-30mm of play before it engages the pressure plate. Is this right? I can't for the life of me see what is missing/damaged on the release bearing end.
Any help or suggestions would be greatly appreciated or if anyone has a diagram of the release bearing that might help. The one in the Haynes manual isn't very clear.
Thanks in advance
Griff

So today i stripped the box out again (getting quite good at that unfortunately) and removed the release armand bearing assembly. Took them down to my local 4x4 specialist and got him to confirm that the mechanical side of the clutch is fine so the problem is hydraulic.
SO i have put it all back together again (apart from front prop to allow access to the slave cylinder) and now i've run out of time! Gotta pick the oiks up from school!
Tomorrow i will try bleeding the system again and see how we get on.