Did you manage to solve your problem with warping discs? Reason I'm asking is because I've got an exactly the same problem on my 530d Msport 2008! I'm on my 3rd set of discs and problem still remains. Got the thrust arms replaced as was told that it could be them but still nothing. Problem comes back after around 1.5k miles. At the moment I'm thinking of replacing brake calipers if nobody gives me a better solution.