BMW aren't going to give any goodwill towards a cracked wheel as they will put it down to wear and tear on our sometimes poor roads. If you take the wheel to a good alloy wheel repair outfit they will fix the crack and paint the wheel and you'd be none the wiser.
I'm down in Kent and we have Diamond Styling:
http://www.diamondstyling.co.uk/contact.html
That do work for Maranellos Ferrari and the like. Their work is very good and they paint the wheel after rather than powder coating which is my preferred refurb method.