Hi ! I have done a couple of threads about brake squeal! For a period of time it was an absolute pain and undermined such an expensive car. I had replaced all discs and pads on all four wheels, the fluid complete brake bleeds, and still had the squeal ( I did this twice with about 10k between the first and second set, with that stupid squeal never going away), I took them off again and used lots of brake pad paste, even changed one calliper completely and still had brake squeal, replaced all of the guides and the anti squeal springs, all with BMW genuine parts and still brake squeal..... was at a total loss,, I then for no solid reason increased the tension on all of the anti squeal springs, even though they were brand new and set to whatever BMW tension spec was, they were a bit of a pig to get on, but it cured the problem never had brake squeal again, Can I say this was the problem ? no but having done all that work and the cost it was only after this that it actually stopped, that is all that mattered to me!!!!
Always said I would go back to a 6 series