Because I really hate it on forums when someone posts my problem then ends it with a totally non-descript 'yea, sorted now, thanks'....
I have solved it sort of; my solution was the user.ini windowed mode edit, and setting the resolution in-game at 1920 x 1080. It's not ideal but it works fine now. I can live with it for now. The brightness in game setting still doesn't work but I'm going to try my card tweaking control centre for that and see how I go. I'll add to this report if I get less lazy and try and make it work any better!
Cheers!