David, I have read through the symptoms you experienced, and although I don't have the eyes on the job so to speak, this is what I suspect has happened.
The quick coupling attaching the pipework from the master cylinder to the slave, has become detached, this results in a solid pedal due to the fluid being unable to exit the master cylinder, and when you press the pedal really hard, the clevis loop at the end of the master cylinder piston breaks.
Now the hydraulic coupling is located directly above the gearbox, and if the coupling is partially detached when the pedal is pressed, then fluid will escape.
What you need to check is whether the clutch master cylinder pushrod is still connected to the clutch pedal, and the clevis loop not broken.
The coupling looks like this..........
The part which I suspect that is broken on the master cylinder, is the thing with the paper tag tied on in this picture.......
Finally this picture shows the position of the clutch master cylinder in relation to the clutch pedal..........
And finally here is a gearbox, to give an idea of where the coupling is located inside the engine bay......
All of these things can be checked with relative ease, and don't require specialist knowledge, and should be discounted before resorting to gearbox removal.
Best of luck
Brian
