Bodie - how come I'm not surprised the RAF is trying to hijack some internationally recognised French aviation terminology?
The correct form is surely "m'aider" in the infinitive - as in TO help me. The PAN call refers to "panne", meaning breakdown.
The difference is in the level of urgency - a PAN (which should always be said three times, just like MAYDAY) meaning that the aircraft is in no immediate danger.
P.S.: yes, French is my native language!