Despite all the arguments in favor of conducting practice pans; why the hell do you have to use an actual emergency frequency!? Is the CAA afraid people are unable to tune 121.5 in a real emergency? There is nothing more frustrating than working in the London TMA, which is already overcrowded RT wise, and having a practice pan on the second set.
P.s. the Practice pan of one UK aircraft can be heard in the entire west Europe region when flying at flight level 370 or higher. Nothing is more frustrating (especially in the weekend), than being disturbed by practice pans every 30 minutes on a 4 sector day.