The plays have endured the years very well and they are the most popular OTR show today, with many sites dedicated to keeping the episodes alive – see links page. The OTR stories have much more humour than today's somewhat glum interpretations, and that certainly lends to the series' success and longevity.
Some of the actors that appear in the film series also make an appearance in the radio plays, but I have only my ear to attest to that. Mary Gordon is often in her familiar role as Mrs Hudson, and Dennis Hoey appears as Inspector Lestrade in one of the earlier episodes. Other actors that appear to be particularly prominent are Frederick Worlock, Carl Harbord and Rex Evans. See the supporting cast page for more details and photos.
I currently have 54 episodes, and I think that's almost all the ones that are known to have survived. Sadly, the majority are still lost, there are rumours that up to 150 episodes have survived but most are not available online as far as I know. I would give my right arm to get hold of a copy of Rathbone and Bruce's The Hound of The Baskervilles six-parter.
All of the OTR episodes are in the public domain, so they're out of copyright and free to download here.
The one chafing thing about the show is the interruptions by the host on behalf of the sponsor – usually Petri Wine – at the beginning, halfway through and at the end of each story. On average, the adverts total about six minutes per episode, so I've removed them from all the episodes in my possession while keeping some of the banter for continuity. I've also edited out the adverts from the 38 episodes starring Nigel Bruce and Tom Conway – you can buy both these CDs here.