Because of the junk on screen I was unable to login and perform further tests.
Is there a launchpad page you'd like me to put this information on?
Still testing! Booted system again. When Samsung BIOS screen appeared again, pressed down both SHIFT keys. Used GRUB to edit the parameters to be passed to the kernel - removed the parameters 'quiet' and 'splash'. System booted, with plenty of text messages (as expected). As the system continued booting, there was _no_ screen corruption. I logged in OK and am about to perform other tests.