In the 1950's Sir John Gielgud and Sir Ralph Richardson portrayed Sherlock Holmes and Dr. Watson on a series of adaptations on BBC Radio. You can listen to a selection of the radio adaptations on Spotify here.
Times Past Old Time Radio also has quite a few links to the Gielgud/Richardson radio dramas, as well as several other radio versions of Holmes (including Rathbone and Bruce).
I'm a stay-at-home dad, and Director of Music Ministries at a United Methodist Church in Mt. Juliet, TN, and a longtime fan of Mr. Sherlock Holmes.