Further to Dan Dare, what about Dick Barton - Special Agent. Which was a daily thriller series on the 1950s wireless in the 5.45pm slot, and was sadly replaced by The Archers - an everyday story of country folk.
And the idea for the Archers is said to have arisen when a farmers' representative, in a meeting with BBC executives, said "What we need is a farming Dick Barton!"
I suppose he meant by that, something which the whole country would listen in to avidly, but which would be about milk yields rather than espionage. In any case, it's a neat quote with which to counter those who (mistakenly) believe that The Archers has become more sensationalist in recent years.