So what is missing from this broadcast intrusion?
Of all the lost media documented on this Wiki and elsewhere, I have to say the Southern Television intrusion is one of the most confusing lost media stories of all-time. For any lost media YouTuber (Blameitonjorge, All Things Lost etc), this lost media has quite the story! TL;DR: Video is a complete fake, audio might be real.
So, most people would assume that all media for the intrusion, audio and footage of it occurring in real-time, is all publicly available. Sadly, this is not the case. Two videos have claimed to be the "real" footage of the hijack. The one most people have watched is the the video using Horton's transcript. However, this video is 100% a forgery. There are a few reasons for this: Firstly, the hijack occurred during an ITN News broadcast at 17:10, not a local Southern news show (there is a TV guide that confirms this, London followed by cartoons: <a rel="nofollow" class="external free" href="https://tvforum.uk/tvhome/40-years-1-day-43147">https://tvforum.uk/tvhome/40-years-1-day-43147</a>). Secondly, notice how the audio does not match with the reporter's speech? This is because the reporter is NOT Andrew Gardner, but Cliff Michelmore (<a rel="nofollow" class="external free" href="https://www.itv.com/news/meridian/update/2016-03-17/our-memories-of-cliff-michelmore/">https://www.itv.com/news/meridian/update/2016-03-17/our-memories-of-cliff-michelmore/</a>). Finally, when the video cuts to the Looney Tunes episode, one can see a Cartoon Network logo at the bottom, CN not even existing until 1992.
There is also a NationSquid video that has completely different "footage" of the intrusion (<a rel="nofollow" class="external free" href="https://youtu.be/AO2d6W9RZPc?t=415">https://youtu.be/AO2d6W9RZPc?t=415</a>). I asked someone about this a while back, and they said it was a fake because it uses a VHS special effect. Additionally, the fact that NationSquid only showed part of the broadcast, rather than, you know, uploading it in full, is quite telling.
But what about the audio from the first video? From what I understand... this is real! Coming from this discussion (<a rel="nofollow" class="external free" href="https://tvforum.uk/tvhome/40-years-1-day-43147">https://tvforum.uk/tvhome/40-years-1-day-43147</a>), somebody not only debunked the video, but also provided a link to the audio. Using the Wayback Machine (<a rel="nofollow" class="external free" href="https://web.archive.org/web/20190129170825/http://tx.mb21.co.uk/gallery/hannington/spacemessage-offair.mp3">https://web.archive.org/web/20190129170825/http://tx.mb21.co.uk/gallery/hannington/spacemessage-offair.mp3</a>), I got the audio to work. Notably, the recording starts with Andrew Gardner breathing before reading the summary, and the actual ending of the pirate transmission lasts a lot longer. You can also hear more of the Looney Tunes broadcast that wasn't featured in the fake video! Two reports, one from Gardner later in the day, another from a radio channel, both of which discussed the incident, were also included. The latter has the reporter read out one of Vrillon's lines, which is almost entirely accurate. I am highly confident this is the real audio, but until someone contacts MB21 to confirm it (<a rel="nofollow" class="external free" href="http://tx.mb21.co.uk/gallery/gallerypage.php?txid=847">http://tx.mb21.co.uk/gallery/gallerypage.php?txid=847</a>), I am not 100% sure.
To summarise then, I believe the audio has already been found. However, footage from the event in real-time has not been, and all videos thus far claiming to be are fake. It is a shame that recreation has caused so many people (including myself) to be misled over the years, since the event is very much historical regarding television media.