Well I've finally got round to putting all the bits together and hooked the HU and emulator up to a PC and everything seems to be great!
The PC is resciving S,s,P,pN,n etc and I can update the DISK/TRACK and Min/Sec via the C and c commands, the only problem is that I cannot get the HU to display text sent via the dxxxxxxxxxxxxxxxxxxx command. I know the HU has recived the data because I altered the code to send a # after it recives th 19th char but when I press Display on the HU the read out is blank. I have tryed sending the text in both ascii and hex with no succsess. The HU I am testing it on is quite old (KEH-P4530R), does it need a particular function (such as CD-TEXT) to display the data? I know it displayed the 7 Char Disk name I configured when it was connected to the cd-changer.
Am I missing something obvous? any suggestions would be great!

Cheers
Chris
You need send to emulator disk and track number, disk and track name. And after this, send 'p' character (play). After this, HU can display disk and track name.
But! If your HU can't operate with CD-TEXT function, this may not work.