The underlying problem is that the /boot/grub/device.map file was missing
Managed to get this working by doing the following.
Boot from the CDROM and run 'Rescue a Broken System'
Run a shell on the root partition
Mount /boot and /var
Run the command '/usr/sbin/grub-mkdevicemap -n'
Run the command '/usr/sbin/grub-install /dev/sda'
Run the command '/usr/sbin/grub-install /dev/sdb' (for completeness - this is a mirrored system)
Run the command '/usr/sbin/update-grub2'
The underlying problem is that the /boot/grub/ device. map file was missing
Managed to get this working by doing the following.
Boot from the CDROM and run 'Rescue a Broken System' grub-mkdevicema p -n' grub-install /dev/sda' grub-install /dev/sdb' (for completeness - this is a mirrored system) update- grub2'
Run a shell on the root partition
Mount /boot and /var
Run the command '/usr/sbin/
Run the command '/usr/sbin/
Run the command '/usr/sbin/
Run the command '/usr/sbin/
Reboot - and it all works