Hey guys thanks for the reply! Sorry here are some more details...
It's a 2005 3.0d with 59k miles.

The battery was removed to be charged and tested, I had just purchased the car and was unaware the you have to lock X5s to prevent battery drain!

The BMW tech is trained and certified, he had the computer on it checking the parking sensors that day and no faults were showing for the radio? He seemed puzzled and said he had never encountered this problem before.

I have since then removed the battery terminals for 45mins to reset everything......no joy. I have removed all related fuses in the boot and glove box to see if they are the problem?
I don't want to go buy a new radio module until I can rule it out, but if there was a fault with that surely it would have shown as a fault on the BMW techs diagnostic tool????
The sat nav screen blinks regulary now and my I pod connection through the cd changer has power as it will charge my I pod.