plant some timber on to finish into. fill the timber. get them to sand it. paint. job done.
12mm proud is a fair amount around a doorway, but it ain't the end of the world for a good chippy. Just make sure you keep the skim as tight as you can by the edges so the 12mm doesn't turn into 20mm!
Personally I wouldn't use a stop bead just in case the edges need chipping away to accomodate the archtrave etc. Just make sure it's pretty even and hardly any skim where the architrave will sit. The architrave will cover this area anyway Â![]()