Thanks for the tips, MITM_Fan.
I don't have HandBrake at the moment, and I will look into AviSynth you mentioned. So far, SUPER has been working fine, with lots of features you can tweak.
I can do a bit of programming, but I'm not too keen on writing scripts or command line stuff right now, though it's nice to have some script ready that works as a sort of default solution for standard-quality vids.
With interfaces, I always make notes of the settings that work best, which can be tedious and can easily get lost.
Rich