I took the screen apart and pulled a few fuses to try and re-set the system, but it made no difference.

Turns out it was the Traffic Master system. These were not specced from the factory. It was a UK option and retro-fitted in when the cars arrived at the docks in Crewe.

I just ripped it all out as I never used it anyway. And everything now works perfectly! I have Nav and a TV again!!