There seems to be a simply staggering lack of understanding here about the reason and legality of training fixes and practice pans.
A training fix or a practice pan on 121.5 is surely nothing more than a means of an instructor demonstrating to a stude how the D & D cell can locate you and direct you if unsure of position. Surely use of this facility is restricted to training flights and genuine emergencies only? There can be no way a pilot, qualified or not, can transmit one of these outside the basic PPL training syllabus.
To suggest that a Practice Pan might be used to ensure you are clear of controlled airspace (unless I have totally misunderstood the above post) is so stupendously unprofessional and such a virtually Criminal abuse of the system that I am astonished anyone has the gall to suggest it here.
If you're terminally lost and out of all other ideas then by all means use 121.5 to restore your plot, but have the guts, honesty and professionalism to admit to this (Pan Pan Pan G-ABCD unsure of position request fix...) and not hide cravenly behind a spurious "training fix" or "practice pan". How sick!
Bear in mind that Professional aviators are sometimes required to monitor 121.5 and spurious use of this lifesaving frequency is not only very public, but also potentially very distracting to those who use it for the correct purposes.