14.04 Upgrade triggers grub-pc failure

I "elegantly solved" my problem by using the following:

sudo apt-get purge grub-pc grub-common
sudo rm -r /etc/grub.d/
sudo apt-get install grub-pc grub-common
sudo grub-install /dev/sda
sudo update-grub

Deleting the /etc/grub.d/ directory seemed to have gotten rid of whatever 12.04 files I had lurking, allowing 14.04 to get on with installing grub!

Although I would of course recommend making a backup of anything that you are about to delete.