Final 3 Greens, I can't see anything in what Wiley and the others said that disputes the legality or usefulness of the current procedures using 121.5 for practice pans.
I'm assuming that Croozin wasn't commenting on that either, but more likely on your extraordinarily offensive tone in telling those 'unlucky' enough not to born with a British passport to take their bats and balls and go play elsewhere if they don’t like things exactly as they are. (I’ve just watched ‘Piece of Cake’ and your attitude reminds me of the way the RAF pilots and hierarchy refused to listen to the American who had flown against the Germans in Spain ‘because that was Spain, and things are different here’.) Take a look at what you said and how you said it and ask yourself whether or not he might have had a point. I certainly thought your comments were offensive.
I know that British pilots find fault and suggest improvements in ATC procedures elsewhere in the world – and rather pointedly at times. (The frequently deplorable standard of HF comms in India immediately comes to mind.) That's their right as users, and sometimes these criticisms get things changed for the better. If you accept that, what in world is wrong with a non-British pilot suggesting that in his or her opinion, improvements could be made to the excellent Brit system?
As useful as the service might be to light aircraft pilots in the UK, like the others before me on this thread, I too find it distracting when I'm in the very busy Heathrow terminal area and someone starts 'practice pan-ing'. Like them, I switch 121.5 off or turn it down when this happens - which I accept is not desirable, as I’m depriving myself and ATC of an excellent, quickly resolved fixup should one of us big fellers screw up a frequency change, as can and does happen.
I accept that a discrete frequency for practice calls would not be easily (or cheaply) accommodated, but that doesn't make the calls for one any less sensible. It's surely indisputable that it would be better for everyone concerned if there was a discrete frequency for practice pan calls – unless someone out there gets a vicarious thrill from making these practice calls on the ‘real’ emergency frequency.