Thanks for the suggestions. I can see what Dave means about isolating one colour channel, and I’ve done it before for short FX shots, but I have about 7-8 minutes of footage to deal with, and a client who can’t understand why I cringe when I see the footage and want to fix it!
Also, I admit, I was feeling lazy and was hoping to find an easier solution. I was sure I’d read about plug-ins for averaging frames over time, for example for noise removal from low-light security camera footage, which I thought might do the trick if applied to just the blue channel. Not having much luck with my searches though.