As a Brit, something doesn't ring true about those accents. Can't quite put my finger on it. Sounds like the stereotypical upper-class Eton type officers with a token working-class cockney for the rank and file gunner.
And like Batz says - you can hear the guns a clear as day, yet when the pilot speaks, the four merlins sat a few feet from his head are at best a barely audible hum? Something doesn't ring true.
And the fact that 'bomb aimer' is not used at all is a bit of a giveaway, as has been pointed out.