This clutch has slipped on and off for the last four years. It is now bad.
I have disconnected the gear linkage, and the rod is hanging down clear of the lever foot. I have disconnected the hydraulic pipe at the master cylinder..
I have attached a rope to the exhaust support bracket and heaved on it. Trouble there is the rope is elastic, and I feel I am pulling against the clutch springs. It needs a jerk or an impact to free it. Glad Andy agrees that rust on unused spline section is likely cause.
I am sensible of the danger of pulling the car off the axle stands if I use the estate to heave. The rear wheels are chocked, handbrake is hard on, and I can put ramps under the front wheels to minimise danger. It would still leave the jack under the gearbox.
There is about an inch gap between crankcase and gearbox.
Wife and I have tried rocking car in and out, me pulling the jack handle forward, she pulling the rope back. All we achieved was to move the jack base forward under the gearbox.