When I'm on a prolonged journey, anything over an hour or two, I start to hear a high pitched whineing metallic sound like when the brake pads are worn down to the metal and the spike on the pads is scratching the disc. It seems to come from the rear but I can't be sure. Once I get to about 60mph it seems to stop but that could be due to road/wind/engine noise. The pads are fine all round by the way.

Any suggestions gratefully received as it's driving me and it's not a good look when driving through a town