You were absolutely correct. I waited two hours then decided to eject the disc. When I ejected it, I then got the could not read disc message.
Anyhow reburnt it, and it worked perfectly. Upgraded from 4-1/42 to 4-1/00.
Very happy with this forum and the great users.
Now only have the splash screen to sort out and my existent/non-existent Bluetooth.