Looks like you need to get at the unit to find the number.
Unless it is mounted where you can see it behind the dash then it is a dash off job. I had to do that to get at mine on the 2002 Plus8. It was screwed to the ash frame high up.
If you do that then take photos as you do the job. With the dash removed you will then have photos of the layout of all units etc. The case of the pcb unit may or may not have any ID on it....mine didn't! GRRR.
I opened the case up and checked the interior...take care! Photos taken of interior etc and hot melt glue to replace the cover. I sent the photos to Graham at Melvyn's. In the end I managed to fix mine, bit of luck really.
