Wow. You lot are amazing.
I was only young at the time, probably about 12, but I was glued to the whole series. I remember Bartholomew Fair being used, and I think Streets of London was used in a programme about something to do with the homeless and dispossessed. I remember being surprised when I heard the song again and discovered how popular it had become. As Bonnie says, ask Ralph. The other reason I think it went out in the early 70s was that I listened to it in bed. I didn't stay up for it, so I must have been quite young.