Bbc Radio 4 have any number of dramas in their back catalogue. One that I particularly enjoyed is Alan Plater’s - available on the Internet archive, I find.
Then Orson Welles original War of the Worlds by the Mercury Theatre on the Air in 1938 is well worth a listen. That is available in several places around the Web.
Then, of course, there is Big Finish, who started off doing Doctor Who audios and have produced hundreds over the years - far more hours than there are of T V Doctor Who, classic and new - but they also produce a lot of other dramas, based on other properties and some completely original.
Overall their earlier ones are where the standout tales are, but they are fairly reliably entertaining throughout.