Now that I have been using the car, albeit not a great deal, I realise the Parking Aid is defective. Probably one or more defective sensors. I may get round to getting something done about it but as I have only done 30 miles since buying the car before Christmas I am reluctant to splash out in case the car turns out to be a polished turd.
I have never had rear parking sensors (well I have, but I always referred to them as the bumpers) so I won't miss them.