While waiting for Atlanta and Marina to finish getting ready for the Stingray reunion party, Troy, Bones and the others gather round to watch some of the old projector tape records of their more exciting missions. While I'm not a rapid fan of this stuff or anything like it, I do have fond memories associated with Stingray, Thunderbirds etc because they used to be on BBC2 on a Friday evening when I was younger (along with things like Man from Uncle, which I also have a soft spot for). So this compilation was a draw for me more out of nostalgia than anything else for sure I could not tell you what was the "unseen" footage and what was the footage I had seen countless times before.
As such then, the party will have limited appeal because outside of the "unseen footage" aspect of it this film is of less value than the actual episodes. This is because the compilation aspect of any show only works when it is a collection of best bits, which this is not really. It does still bare a viewing though because it is entertaining to look back on Stingray but as a "new" episode it is not that great. Of course to fans it will be a joy to see their favourite characters "back" and the offer of unseen footage will only increase this. Personally I would have liked the "watching the film" scenes to have been a bit post-ironic or at least tongue-in-cheek but perhaps this would have annoyed real fans who are the target audience at the end of the day.
Overall then, a so-so episode of Stingray to the point where it is not worth starting here if you have never seen it. However as a "reunion" it is worth a look for the chance to see the old characters brought back in footage some of which has not been seen before.