Don't sweat on the side sills Matt - i have parked my car next to a coupe with the full AMG kit at the local stealers, and they look absolutely identical. At the parts counter they tried to convince me there was more of a curve to them - but stood right infront of both, i really couldn't tell at all.
That's really good to know, thanks.
The existing ones will have to do anyway, as no one has any used ones & judging by aftermarket prices, I expect them to cost in region of £400 up +vat from MB! That would almost be more than my combined cl203 mods so far!