Did I seriously just see 275 rears on a 520d.
Of course you did, its the same wheel/tyre size as standard across the M Sport range, just like you'd find 265 rears on an 18 inch fitted E39 520i Sport 10 years ago. The wider rears are largely a cosmetic thing anyway.
Nice writeup Gibbo - the standard spec of the F10 is excellent and much of the things you've listed are standard fit across the range - inc USB etc. You had Business Nav too, there is a full widescreen Pro nav available above this.