5. One piece of input suggested that the wiring loom from a left hand to a right hand vehicle (the new unit came from a German Astra) may be a contributory factor but we still have to deal with the fact that the buttons connect to the display at the top of the screen in all the cars so no option to put in upside down.
Wiring not an issue, Buttons at top is a good sign.
Query - does the back of the display unbolt and get turned round which may correct the problem?
As I said, possible, but would require a deliberate effort, as it would have to be rewired. (i.e.not likely)
Th LCD itself can be set-up to invert its display, but it requires different voltages on the interface connector which could come about as a result of an electrical fault. Ergo faulty unit.
If you're dealer is willing to give it another go without charging you, try re-programming it, otherwise it's safe to assume it's faulty and send it back.