No radio, Cd changer but sat nav works....BMw tech cant help

[d6moff]

Hello guys,
Please can anyone help, im just back from my BMW tech and he is clueless..?

the problem started after my battery was removed for charging, once it was re-intalled I had no power to my radio/cd changer, my sat nav works but with no sound?

I have checked the fuse in the glove box and the two in the boot...they seem fine, are there any others?? I have have a quick look in the radio module and that looks fine....nice and dry no water ingress

When I am driving the sat nav screen does blink briefly now and then......?

Can anyone please offer any advice as a car without a sound system is very dull......I have disconnected and re-conntected the battery terminals since then and no joy...