Well, 7000 miles of exuberant driving and a reasonably (ok very) aggressive track day saw my brakes making a humming noise in use. No depredation in braking but an annoying humming noise.
After much investigation my dealer can’t find anything wrong but acknowledges the humming noise and BMW Germany have told them to just replace all my pads and discs under warranty to be on the safe side.
So, all new brakes for me tomorrow for free!