Brilliant pictures as always GLLOQ !!!!
It seems that you must have just about rebuilt everything mechanical on your machine, fantastic.
I agree with your approach re preferring to get the mechanics "right" but I am truly a muchanic with limited skills. In this case I will look to just replace with same or repair.
As it isnt quite broke yet I do have some time to seek a replacement. (Having said that it will probably now fail !!)

Thanks again for pictures. Good to see that the cylinder can be taken up to a reasonable place to work on. I was concerned about getting fluid everywhere in the footwell.

Did you bleed the system after? My car is an early model with the slave cylinder inside the bell housing. I just hope that the issue is the master cylinder and not the slave !!!!!!

regards
nigel