I can't remember what they were called. You got a large plastic (red) 'briefcase' style box with a cassette tape that narrated a story and then I think once a month or fortnight another tape would be sent. Some were classics, I remember one being Jack and the Beanstalk. Others were stories I'd not heard of. I think I ended up with about three 'briefcases', and I remember wondering why two had a picture of a boy on the front and one a little girl. I got hours of amusement out of them.
I've just been reminded of this on the 'films you see differently as an adult' thread as 'The Little Match Girl' was mentioned, and that was one of the stories.