Spent a few hours with the car today, removed the transmission, bellhousing, and pressure plate/clutch disc.
Lots of dirt and grease inside the bellhousing - which I suspect is due to a leaking slave cylinder. There's a little weep hole in the rubber bellows of the slave, and it was leaking fluid quite readily when manipulated.
Slave bellows:
Bellhousing:
Black Tag ZF6:
Clutch disc, surprisingly good condition for the miles. I am going to have to look through the service records, I can't see this being the original clutch disc.