Good news, sort of. It would seem that the problem is down to the fact that i have my tunes on a usb harddrive to which i created a symbolic link in the /var/lib/mythtv/music folder.
So to test i copied a folder of mp3s into the /var/lib/mythtv/music folder and using chmod set the permissions to 777. This then allowed the server to pick up the music. However i dont really want to move my music off of my external hd, so can any make a suggestion as to what to do?