A lot of time has passed and I did indeed solve this and another clutch problem with the car and it has performed faultlessly in the years since. To save me attempting to remember every detail and type it all again, please read the following topics in the order they appear.

Clutch hydraulic issues:

http://www.peachparts.com/shopforum/tech-help/94692-final-chapter-190e-clutch-saga-i-hope.html

http://www.peachparts.com/shopforum/tech-help/106387-190e-clutch-saga-epilogue.html

An unrelated clutch issue due to failure of the dual mass flywheel:

http://www.peachparts.com/shopforum/tech-help/156497-two-mass-flywheel-failure-anyone-else-suffered.html

http://www.peachparts.com/shopforum/tech-help/114385-clutch-rattle-w201-m102-2.html

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107.023: 350SLC, 3-speed auto, icon gold, parchment MBtex (sold 2012 after 29 years ownership).
107.026: 500SLC, 4-speed auto, thistle green, green velour.
124.090: 300TE, 4-speed auto, arctic white, cream-beige MBtex.
201.028: 190E 2.3 Sportline, 5-speed manual, arctic white, blue leather.
201.028: 190E 2.3, 4-speed auto, blue-black, grey MBtex.
201.034: 190E 2.3-16, 5-speed manual, blue-black, black leather.