If the car was mine, I think I'd start by reading up on how to 'initialise' the mirrors - plenty about that on the web. This is necessary if the battery voltage has become low for some reason or the battery has been changed. Curious things can occur if the mirrors were preventing from opening or closing at some time - perhaps due to ice or whatever.
Next, there could be a broken wire in the harness where the bodyshell connects to the door - repeated flexing can cause the wire conductors to snap whilst leaving the insulation intact. Sometimes you can feel a lump inside the insulation where the fracture has occurred.
Next, there are devices called body control modules that attend to the electrical systems all over the vehicle. Sometimes there is only one, but the C5 for example has one per door
This will probably ruin your sanity, in which case a chat with the Citroen service manager could pay dividends - hopefully they may have come across this before.
Wishing you luck with it!
This is what happened to me last winter......a passenger tried to use the electric windows when they were frozen shut. Afterwards when things had thawed I was able to initialise things once more courtesy of the handbook. However, the mirrors wouldn't fold in either
Anyone who can tell me the connection there wins a cookie!
John