I have not looked into the M3W clutch system in detail but most manual clutches work the same. Has your clutch pedal got a few mm of free play when fully off before it starts to pressurise? I sounds as if it is not coming fully off and opening the port in the master cylinder to the reservoir. This port should depressurise the system with the pedal fully released, there should be no pressure in the system with the clutch pedal released, no "preload". As you depress the clutch pedal, the reservoir master cylinder port is closed off first and then the system pressurises and moves the slave cylinder to release the clutch. There is an adjustment for free play on the master cylinder push rod. If that fails check the master cylinder for an internal fault before getting into the clutch, much easier and cheaper. I hope that helps.
