Bavarian BMW, Belfast - have got back to me and said that they get loads or rims in with similar cracks and when the test them they are always ouside the tolerances which inidicate a hard knock.
I can't be arsed fighting with them so am gonna get the wheel welded and hope that it doesnt crack again.
Last: 330cd Sport - Silver Grey, 335d M Sport Coupe, F10 535d M Sport.
Current: AW F21 M135i, Coral Red, Pro Nav, Vis, HK, & Clunky Adaptive Suspension
Current: F15 X5 XDrive 40d M Sport - Space Grey, lots of toys.