Thanks, turns out it's included with GWX 3.0 Gold anyway lol.
Tried installing again and the game now works, but I can't get Rubini's widescreen fix to work. All I get is "can not start 3d engine" or something like that it won't even load up

.
Life is so unfair! lol
EDIT! FIXED!
Seems SHIII doesn't like running at 59hz... changed to 60 and its fine. Now to install my other mods and go give the brits something to worry about!