Vw Passat 2000 Alloy problem

The alloy wheels on my 2000 passat are corred in several places
i have had it back to the dealers but they informed me that they are not
covered under vw corrosion warranty.
Has any else had similar problems with these alloys ( they are the Audi High
Chrome Ones So the Vw dealer tells me).
Also does anybody know of a company in Lancashire that can sort out these
corrosion spots.
Any help would be appreciated.