Three 30' Agatha Christie short story full-cast dramatisations: In a Glass Darkly, about a man who sees a murder in an old mirror, The Dressmaker's Doll featuring a doll that has a life of its own, and The Case Of The Perfect Carer (retitled from The Case of the Perfect Maid) - where a non-existent maid is blamed for a spate of burglaries.
Agatha Christie is the acknowledged 'Queen of Detective Fiction'. Nearly all of her Hercule Poirot and all of her Miss Marple novels have been adapted for BBC Radio and released by the Radio Collection.
These are non-Marple/Poirot stories.