Ozthai,
As an Australian male (Personal Profile) you could well come in for flack from PPRuNers when you say you are teaching standard English.
Seriously though, it is not clear at what stage in their ATC training you are trying to introduce emergency phraseology. If this comes before proper ATC lessons start, then it is understandable if the students have only basic knowledge. However, if your lessons come at a more advanced stage of the course I would have thought training in emergencies would have already covered alot of the phrases you refer to. Does your training set-up include something like our mandatory TRUCE (Training in unusual circumstances and emergencies)?