Not sure if I’ve missed this elsewhere but it appears that the UV Pass when rendering a UV pass only doesn’t actually save the UV Pass, and it saves the combined image instead ( which I had disabled). Using - 2.54 beta.
Also it crashes when saving Open EXR and checking the Half box and trying to save the UV Pass.
So now I have to (apparently) manually save each frame of my animation after manually selecting the UV pass layer.
Correct me if I’m wrong please 