A good paint I have used in the past for the BBS silver is Plastikote Chrome Paint. It dulls (i say dulls, it just looks better) down nicely after a day or so and blends in well. Has reasonable gloss too so it looks pretty good
On my old BBS, VW Satin Silver was a pretty good match, but the Plastikote appears better.
Halfords sell it in little pots :) Just make sure you give it a good stir prior to applying it.
How bad are the marks?