[Avulon]

The left hand unit in the boot is the video unit, this will come to life as soon as the car is unlocked, or if already unlocked as soon as any door/boot/bonnet is opened (it takes a while to get going, so starts asap). The noise you can hear is indeed it's own cooling fan.

The Nav unit (GPS) in the side of the boot also does the same - coming on as soon as possible. If the car isn't started and nothing else is disturbed the video unit will shut down after 30 seconds - 1 minute. The nav unit will shut down after about 5 minutes.

It's common for the nav unit to fail to shut down properly. Interfering with the setup should only be done with the battery disconnected, and the battery should only be disconnected once the nav unit has shut down: that's if it does shut down. Remember disturbing anything on the car will restart the timer so it's important to open the bonnet and boot and then close the car door and wait for the nav to shutdown and only then disconnect the battery. I bet most non-rover garages won't know this: hence the reason for so many 'bricked' nav units.

If everything shuts down properly as described above then the problem with the head unit buttons is probably down to a broken Ibus connection somewhere, or one of the unit's is at fault. As the steering wheel controls seem to work then we'll rule out the radio unit for now (the one on the right in the wheel well. With everything shut down and the battery disconnected use some radio removal tools to slide the nav unit out and disconnect the two connectors at the back. Now reconnect the battery and try again, if this doesn't work then it's down to tracing the wiring for a fault and or substituting a known good head unit to try and find where the fault is. It's unlikely that the Video unit would cause the problem as the messages (button presses) are sent from the head unit to the radio and Nav unit only. The radio and nav then communicate with the video unit.

Hope this helps.