I just did it! After many many many tries getting it off by hand I had a bit of inspiration and gently used a snap on strap type oil filter remover and a short breaker bar. Pushed it in, pulled on the breaker bar and with very little effort it was out. How do I make this information easily available to anyone trying to overcome this problem?
Hi - just a quick comment;
Rotate 90 degrees and pull off. Don't remember in which direction to rotate, 50% chance of getting it right first time. Doing it wrong is not possible since then it just don't rotate.
Applies to both master cylinder attached to clutch pedal and slave cylinder on gearbox. Master cylinder is a tight fit, there is not any room for hand to grab and rotate. What I did was to grind a slit off a (think it was) 32 mm 1/2 inch socket (ratchet/pipe). Looked a bit similar to tool for undoing a catalytic converter oxygen sensor. This I slit the socket onto the master cylinder and used the ratchet wrench to rotate. Worked first time. Used the same socket to fit the new master cylinder by pushing it in a rotate opposite direction from removal. Bobs your uncle - is'nt that so ?