In fact after accessing the M Drive through the CIC you need to press the Options key. This will give a menu for M setting as well as M Key Settings. Then you change it. Switch off ignition, take the key out, and put it back in, and restart the car.
I after the nudge from M Ryder, I had to go and figure out myself. In fact thru the options, you can also reset the M setting. Greater options.
2007 E92 6MT - Silverstone II with /// Performance Exhaust with ACM Test Pipes and BPM Sport Stage II Dev-Tune
2011 F25 X3 3.0d