I am attempting to scale the glyphs as a group down to a smaller size [not UPM] and have done so but an unable a way todo it while scaling metrics and side bearings at the same time. Is this possible in Glyphs or must I manually go back and reconfigure side bearings one glyph at a time?
You can do that by scaling the UPM. This thread has information from Mekkablue about that:
But then my UPM is wrong. Do I have to scale the UPM down to the size that I want, then rescale the UPM back to 1000 without scaling outlines?