Good morning Nelz,
Thanks for the follow-up.
For the last few days I've been using "e" at the grub boot menu, as per your suggestion, to edit grub on a temporary basis. As per the systems original message I set the gfxpayload to 1280x1024x24,1280x1024. I also removed the "vga=..." setting from the end of the line that started with linux and pressed F10 to continue booting.
This seemed to get rid of the original "vga deprecated" message at boot-up, so this morning I bit the bullet, logged in as root and used "Kate" to edit /etc/default/grub. Once again I set the gfxpayload to 1280x1024x24,1280x1024 and removed the "vga=..." setting from the end of the line that started with linux. This was saved and then, in a terminal, having cd'ed to /etc/default I issued "grub2-mkconfig -o /boot/grub/grub.cfg, as per your suggestion.
The rebuild of grub seemed to proceed without the generation of any error or warning messages. However, on rebooting the system the original "vga deprecated" message reappeared. Once again logging in as root and cd'ing to /etc/default I used "less" and thereby found out that grub.old and grub.original both have the "vga=..." setting intact.
Do I now have to manually edit grub.old and grub.original as well ?
Should I even be going near these files ?
Aren't these files somehow generated by the grub2-mkconfig process ?
The system still boots, touch wood. I can still use the desktop and even get on the web, as you can see. This means that thanks to your guidance I have not yet borked the system.
Any further help that you can give with this would be very much appreciated.