Search on "radio dramas" in the bar regularly until "radio dramas" appears in the capsule shaped in the listings for you; you might want to try "BBC Radio" too. I'm a old fart Brit bought up in the golden era of BBC for context.
I adore le Carré and there are quite a few read by him, some quite abridged. However, these will probably stop you going to sleep because you stay awake trying to guess what's actually happening.
RD Wingfield
the Whitehall 1212 series about the old Scotland Yard are half hour stories of the old type where the criminals always give themselves up and explain why they did it!
Paul Temple (and ..)
Miss Marple.. and related Agatha Christie
Dorothy L Sayers (Lord Peter Wimsey)
The trenchcoat PI with the classic American Private Investigator voice and demeanour. Damn. Can't remember the name. Philip Marlowe.
there's a Nordic series too: Martin Beck.
PD James.
I hope that's of some use. Don't hesitate to write if you listen to a good one i may have missed!
It's difficult to provide channels because YouTube takes channels down for some reason and they reappear under similar names or not at all.
Send them a few pennies if you can or at least like and subscribe.