I have some interest in this particular mission, seeing as my father was on HMS Coventry, and I run the HMS Coventry website.
I have no doubt whatsoever the audio file is a poorly done fake.
From accounts I have read from the pilots involved, strict radio silence was the order of the day and this was only broken when their targets were sighted, with a short amount of on-air jubilation that was cut short by one of them reminding the others about radio silence. There certainly wasn't 15 minutes of jabbering, which would have been suicide for all involved!
Furthermore, during the recording you often hear more than one voice talking at once - radio simply doesn't work that way, it's one at a time. Additionally VHF is line of sight, and as they were at wavetop height with no friendly units nearby and no AWACS, who on Earth would have been managing to both pick up all this audio and record it?