OK, the orginal "flat" rear core was part no: 3C5 827 469
C ULM. This was dropped end of Sept 2007, and superceeded by 3C5 827 469
D ULM. Those dates & part numbers are for dealer supplied parts though, so factory fitted parts may have different dates. Furthermore, if anyone has had the early type rear badge replaced, under warranty or otherwise, for the worming, then you will automatically get the latest version.
For the UK, the rear core assembly is around £76 plus VAT. Another option would be to visit a scrappy and get the rear core from a bent Golf !!!