You may well teach the queens english to foreigners but they revert to their own language syntax.
One has to try and think how johnnie foreigner thinks.
I had absolutely no problem understanding the GIG controller unlike my first trip to JFK in the 70s but then I had an experienced crew who briefed me on what to expect and translated when I didn't understand.
In BOAC there were briefing notes on what to expect wherever we flew in the good old empire....
My last company who incidentally were the first to fly direct from middle Europe to GIG had similar briefing notes....
That neither crew member understood controller in spite of flying for 12 hours smells of a lack of professionalism in my book.
And what would they have done steaming along at three grand with a radio failure....