If you don't get anywhere with the dealer, you can always have them refurbished.
The 313's on my previous E90 (well the 2 that never got refurb'ed) went for 3 years and over 60k miles without any corrosion or marks appearing. And I used wonder wheels loads of times, as well as bilberry and various other wheel cleaners of varying toxicity.
2012 Alpine White E92 335d M Sport LCI | Coral Red Dakota Leather | Media Package - BMW Professional | 313 Wheels | Evolved |
Previously - 2009 Alpine White 325d M Sport LCI | Auto + Paddles | Media Package - BMW Professional | BMW Performance Front, Sideskirts and 313P Wheels | Black Grilles |
Carbon Black E46 ///M3 '04 | Manual | Evolved |