@Clyde Thanks - managed to create an image backup so I'm happy now :)
But unfortunately I still haven't resolved this audio issue; do you have any pointers? From memory I don't think I've ever used OMXPlayer for video previous in the past, but as of recently if I don't use it then videos take ageeeees to load, so I have to use it, it would seem. But I can't for the life of me figure out why the audio won't work! As mentioned before, I'm trying to get this working through HDMI.