Could be something as minor as a low battery causing the problem, which I would try first, or a trip down to the dealer . Once again the UK site may have recommendations as to which dealer. Discovery Sport Forums - Forum for all Discovery Sport Owners
A blocked camera would cause all these issues. Clean in front of the camera with windex. Then look into the camera to make sure nothing is trapped between it and the glass. The camera is in front of the rear view mirror.
After you make sure the view path is clear, reboot the car: get out of the car and lock it. Wait for the the nav unit to turn black and flash off. Then open the door and start the car. Good luck, I hope you have nothing actually broke!