So despite the aforementioned reset procedure, my console continued to display (sorry for the pun) demonic tendencies.
It turned on and off at random, froze and displayed vertical lines, as well as freezing and staying on when the ignition was turned off and the doors opened!!
A visit to my Chevrolet garage resulted in " you need the screen replaced and it's a common problem"!!
So on Monday, I am getting it replaced and will keep you advised.
One question..The service guy at the garage said the screen had a flash memory! So is the Sat Nav data etc..stored on this flash memory?? If so, I will need to ensure all updates are reinstalled.