Heathrow Director says on page 3
During my 31 years in UK ATC I was never trained to, and never trained anyone, to even think of using 121.5 to contact an aircraft when the normal frequency was busy, or for any other reason.
I'd say that on one on four flights through western European airspace, I hear Rhine or some other ATC agency calling up on 121.5 to some errant aircraft, instructing him to call them on xxx.xx.
Back to the main nub of the argument: no one is complaining about a GA (or any) pilot calling up on 121.5 if he's unsure of his position. However, it's the "Practice Pans" on that same emergency frequency that most non-UK pilots find a bit unusual.
I think I would be pretty safe in saying that this use of an emergency frequency as a training aid is something that happens nowhere else but in the UK. People trained in the UK grew up with it and don't find it a problem because it's what they've always been used to.
And yes, I leave 121.5 on and up in the Lambourne hold and on finals into Heathrow, (as per company SOP, it's always selected, except briefly, when that radio is used to contact the company or perhaps get an ATIS).
Did I say 'always'? That should be amended to "...except on Sunday afternoons in mid summer going ointo London, when the frequency is usually aclutter with "Practice *** PANs"!!!"