Lost left channel in my P5's and opened before sending them to be repaired (self caused issue). I couldn't find any information how to open them and after spendin a few hours looking at B&W release/ad video I understood the structure well enough to open them and see what was wrong. I located the problem to be in the element (I guess either the voice coil was bent due to drop or the magnet misaligned from pressure by the metal axle.) So I would avoid pressing the headphones too hard against the ears. The metal body looks a bit cheap imo, good thing the finish is great on the outside.
Did you ever get them fixed? I am purchasing these headphones next week and can't wait. :D