Don't know I'm afraid, but aren't SD cards generally used for music storage nowadays? IME cars are only fitted with relatively small capacity hard drives and a large SD card could be much the same size as the free space on the HDD (ie free after the space for maps has been used).
Thanks for that. The BMW I have now and the XF before that both had hard drives which I dumped all my music on so I just got used to doing it that way. I have a big memory stick that I used to copy the music so as you say with all the USB ports on the iPace I can just stick it on of those. Cheers.