Thanks for the tips guys.
I downloaded NVIDIA Inspector 1.9.4.2.
Tried a lot of different settings and found IL-2 wouldn't load up to the menu screen a lot of times, it'd just flash Il-2's main menu then crash back to desktop and I'd have to use Windows Task Manager to shut it down. Sometimes on repeated tries the settings would stick and sometimes they wouldn't. I don't know why, but I've seen that sort of thing before when adjusting driver settings so I just put it down to the temperamental nature of such things. I wouldn't blame it on the 'NVIDIA Inspector' program itself, which I found to be a good program, well set out and easy to use, with lots of settings available to adjust. I'll still keep 'nHancer' installed as it has some other features I might use, but 'NVIDIA Inspector' is definitely a keeper.
In terms of the settings themselves, changing the Antialiasing setting to '8xSQ [Combined: 2x2 SS + 2x MS]' was enough to practically eliminate the jaggies on the cockpit instrument dials, while still giving me about 40-50fps looking at the panel, and 30-40fps looking around outside the plane.
However, with a GTX285 and using my preferred in-game settings, my frame-rate drops to the mid-teens over the more graphically demanding terrain (eg. over palm trees on the Pacific Islands QMB map). So, I'll probably just stick to jaggy old 8xQ AA and getting 40-60fps everywhere. I couldn't find a lower setting or combination of settings than '8xSQ [Combined: 2x2 SS + 2x MS]' that would fix the aliasing on the cockpit dials.
Anyway, thanks again, now I've got a way to get higher quality screenshots, and another way to justify upgrading my video-card (damn it
).