I have a book of Fiat dealerships (across Europe!) amongst my collection of Fiat stuff somewhere.... Not sure if it shows numbers for each dealership, though.
Edit: it does show numbers. I'll have a look for you but don't fancy spending all night looking!
Edit 2: Interestingly enough, it doesn't show codes for UK dealers, only their names and addresses.
Edit 3: Seems it only shows codes of Fiat dealers in Italy =S
There's a 47841, a 47022, 47023, 57030, 47042, 47100, 47852, 47853, in Italy.
But I'll be there all night looking for the one you want! Sorry!