I have made this post as an information post. I recently had problems with a clutch judder but carried on driving with it as it wasn't that serious. My wife took it out and when she came back it was making a loud clicking noise when the clutch pedal was down. Now I might add this car has 38k miles on it and it's had an easy life! anyway back to the noise which went away when the revs went up. Two mechanics said they thought it was the thrust bearing but I wasn't sure about that as thrust bearing noise normally quietens when the clutch pedal is depressed but I knew the clutch would have to be changed. So after it was changed I looked at the old parts and I've never seen in all my years a pressure plate separated from the machined faced ring! two rivets out of three were broken and for that to happen on a low mileage car is lame to say the least. SO if yours clicks on the pedal depression but it goes away with more revs or engaging then it's more than lightly this problem! the centre plate and the slave/thrust bearing were all replaced for economy 

there is always going to be one or two unusual type failures which you wouldn't expect. I had a mk1 fiesta which one day suddenly developed severe clutch judder such that i couldn't drive it as it felt like the judder was going to make the engine fall out.

took it apart and found the diaphragm spring in the clutch pressure plate had broken, one break between the outer edge and one of the slots.

diagram:

http://srmncrauto.blogspot.com/2015/02/diaphragm-spring-clutch.html

I also had a opel kadett (the one like the vauxhall chevette) and the fulcrum ring broke on that.

It's a pain have to remove gearbox to do this stuff.  I had a Vauxhall cavalier mk2 which needed a new clutch and on those you can get the clutch out without removing the gearbox. Shame not everyone makes it that easy. (undo cap on end of gearbox, screw something into end of shaft, pull it out - the other end of that shaft goes through the clutch. then remove cover on bottom of bellhousing which allows access to clutch - you have to turn the engine in stages to get to each bolt. Brilliant idea for making our lives easier when clutch needs work