To answer some questions I have received.....
(i) Yes the wheels appear to have been refurbished by BMW. I bought the car in mid 2007 from Synter Solihul. I only actually noticed early this year when someone mentioned the wheels are regularly refurbed.
(ii) Yes I replaced the front brake pads a couple of months ago so had the wheels off.
(iii) The outer "lip" is painted the same colour as the inner star being silver, hopefully the pitures depict the colour.
(iv) I used some wonder wheels on the wheel inners and while that has removed all the dirt there are patches of corrosion on the insides although you cannot see it when fitted (and covered in brake dust) and it will not spread to the face of the wheel.
(v) There is no corrosion on the star spokes.