Back in 1986 a college friend bought a pack of science fiction stories on a series of audio cassettes. The cassettes MAY have been different colours, i.e. one green, one purple etc. I think there were at least four of them.
Each side had one story per side, each maybe 15 minutes long. The stories weren't read, rather there were multiple actors each voicing a part. It's possible they were from a radio series.
The accents were British and the at least one of the stories was set in Britain, so I'm guessing the series was British. The stories were set up so that each had a punchline/sting delivered at the end.
I can only remember the plots of some of the stories:
Story one: A psychiatrist is interviewing the sole survivor of an expedition to an alien planet. The story is told in a series of flashbacks where the patient tells the story of the expedition's capture by a mysterious, malevolent being who had servants/slaves called "droles". One by one the captives are killed in order that the captor can study the humans and ID weaknesses. The captor's voice was very deep and vaguely Dalek-like.
Eventually the psychiatrist convinces the survivor that none of it happened and he's suffering from survivor's guilt (or something). The story ends with the psychiatrist monologuing his report. Slowly his voice changes and you realise that he's been the malevolent captor all along and that this was one more test to confirm human weakness. The final line is something like: "The subject will be disposed of as food for droles and we shall launch our invasion of Planet Earth."
Story two: In England somewhere there has been an outbreak of spiders. Small at first, they've been getting bigger and bigger as time goes by. The story is narrated by a late teenage boy. The boy's elder brother is working with a Prof at Uni on the spiders. The elder brother is visiting the family for the holidays with his girlfriend, Sheila. The second last scene has the family on a picnic somewhere where the ladies set out the food while the men do more manly stuff. They are attacked by spiders, by now very large.
The story ends with the family in a house under siege, the narrator is called to man the barricades by a parent and says something like "I'll be right there as soon as I've finished recording this." There's then a click as he turns off the recorder. Now that I've written all that out, it sounds a bit Blair Witchy.
Story three: I don't remember much about this one. There was a mysterious plague; the origin and transmission of it was uncertain. The story ended with some weird noises and then a high pitched voice saying something like "We jump from host to host by sound waves. By listening to it we have now infected your brain."
Thanks in advance.