Update on the stones (rocks) getting stuck in my Z4 G29 M Sport brakes.
In the first 1,270 miles of driving my new Z4 M40i I got rocks trapped in my M Sport (front) brakes 5 times and it was an absolutely horrendous experience.
I am now pleased to report that I have had no more occurrences in the last 1,000 miles. I think as the initial stickiness of the Michelin Pilot SS tyres wear off the problem becomes less prevalent. Keeping my fingers crossed anyway.