That's exactly right. They "upgraded" the RCD300 early last year to be MP3 compatible - which will be printed just above the CD slot. Mine wasn't, but I managed to pick one up from eBay quite cheaply and simply switched it over.Thanks for the reply.
I've done some googling, does yours have MP3 printed just above the middle of the CD slot?
Mine doesn't, and some other VW forums have suggested it needs to in order to work....