A bit of experimentation later (and a quick upgrade to 2.78... which promptly ate all my settings. Bah.) and the EE GR2 files' UVs are loading fine (although I had to invert the Y-axis of at least one of them), but the D:OS II ones seem to be missing them. I admit it may be just a
little unreasonable of me to expect everything to just magically work at such an early stage so just put it down to my curiosity getting the better of me!