These episodes have no theme music whatsoever. Each episode begins with just a single "ballad" verse about what is going to happen in the episode. The tune is a version of "Early One Morning." So there are a few possibilities:

Theme music was on UK TV but not US, or vice versa. Or the theme music was added later in the series. Or the theme music was for some reason taken off the DVDs.

I suspect the theme music was added for the US showings of the program, then possibly retained for subsequent showings in Britain. The theme song was by the same guy who had done "Davy Crockett," so it is unlikely to have been in the show as orignally produced in Britain.

Maid Marian in her first episode was not Patricia Driscoll, but Bernadette O'Farrell.