I don't get grinding but I do get horrible loud squeaks every now and again. If I brake lightly, I can hear it quite loud. Prior to my ownership, it was serviced by BMW 2 days before. I picked it up on the road test but they could not find anything.
My guy has since had a good look. Copper grease on the back of the pads has made no difference. For now, I am learning to live with it.