Lost me clutch, thoughts?

Gears, mainly 1st and reverse were getting hard to engage for a while then suddenly got worse, especially reverse one day, then...weirdly...it was OK again on the same day, crunching then..no crunching?
Next day(yesterday) it started crunching again and as I had a bit of excess play at the pedal I adjusted the master pushrod. Great, slipped into all gears lovely (1985 110 LT77 box btw). Later on that day it started crunching again then the pedal went to the floor and stayed there, no clutch at all now. I lifted the pedal back up and it would only go half way down before going rock solid, still no clutch. Got home by cranking it in 2nd gear until it fired, luckily I was only near home on a quiet road.
Nothing amiss visually so removed the master and all that looks good, seal, bore etc, no loss of fluid, then I removed the slave and that looks like new too. I looked into the hole for the slave and put as much pressure by hand as I can on the pushrod and it doesn't appear to have punched through the clutch arm. My next thought was to use a big G clamp to try and compress in the pushrod and see if the clutch disengages, proving a master or slave issue, but I couldn't get the arm to move but sort of expected that as the cover plate needs a leg and hydraulics to move it after all.
I've ordered a new trw master and slave anyway but hoping it isn't a box out job. I can feel the clutch arm moving and coming up against the thrust bearing ok. Clutch fluid was black.

Could be the clutch flexi pipe has delaminated inside, result black fluid and possible blockage. Remove pipe from slave and see if fluid will flow from master.