Ok All, I have just come back from work and while I was sitting in the cruise, I went through the text in the Jeppesen. The following is from Aeronautical Telecommunications, Annex 10 vol 2. Section 5.3.1.2.1. "At the commencement of any subsequent communication in distress and urgency traffic, it shall be permissible to use the radiotelephony distress and urgency signals". There you have it, It is a recognised ICAO procedure to prefix with mayday or pan, if you so wish. My Company in light of our exprience now use this method as SOP's. You must do what you feel is best on the day. I hope you never have to use it for real. Happy landings.