As an RT examiner I would obviously look for a full CAP 413 standard Distress Call, however in real emergencies such as engine failure i suspect this would be difficult unless practiced regularly due to the concentration of flying the aircraft/time available. (rightly so).
My last engine failure resulted in a pretty standard distress call, but only because I practice most days with students. Most other real distress calls I have heard are very basic, Mayday x 3 and who what where - perfectly good in the circumstances.
KK