Clutch Master Cylinder replacement 'hints'

Suddenly after bleeding the clutch circuit last night, I no longer have any pedal pressure. I had a new slave last year, so I'm assuming it is the master this time. And yes there is fluid in the resivoir.

Is there a definitive way to check which cylinder is at fault?

Does anyone have any tips for an effort free method of replacing the master clutch cylinder. Just to start with I have sprayed some penatrating oil on the 2 mounting nuts tonight.

Thanks in advance.

Secondly, is there a way to prove that it is the master at fault without removing it because it certainly looks to be in a very restricted area. Symptoms are that the clutch pedal just goes to the floor with very little resistance at all. Bleeding just passes goo fluid with no bubbles and slave was repleced last year and I can not see any leaks on the garage floor.

Thanks in advance.

Had the same when my master went on the way to Curborough ,pedal straight to floor ,the spring had gone.Can't help on tips as I had it recovered to the jagman .Didn't cost much though so can't be too big a job .