The problem was the original driver was corrupted and although I found the box and cables the installation CD had vanished.
I managed to get a link to download it from Blackvue UK then used the updates linked from here and it's working again.
At the moment trying to hardwire it into the car, avoiding CANBUS. It seems to work on a switched circuit for the rear screenwipe. Now all that's needed is a set of toriz drivers to add an earth. The whole car looks put together with them. Being a luddite I've only just got away from Whitworth to A?F spanners.