It all depends on your school of thought. Gloss first, then any emulsion that gets on the gloss can be easily wiped off (not so easy the other way round)
Traditional way is to emulsion first then gloss. I usually emulsion then gloss. I find it easier to cut in gloss paint than emulsion (steady hand needed). Plus with the emulsioning first, the only part that needs cutting in is the ceiling line. Door frames, window frames etc don't need to be cut in as carefully (unless these are being stained)
It's quite usual for painters to overlap the emulsion slightly onto undercoated wood (to ensure a good seal) then lightly sand the woodwork before top coating with gloss.
I much preferred the pre 2010 gloss paint (with the higher VOC's)
Bloody EU again innit.