I think the tune, called "Popcorn" was used in a schools program in the 1970s. Or perhaps in the timer thingy which was on screen before the shows started.
Unfortunately, Jay70, your memory doesn't serve you correctly. The Great Egg Race's theme tune had a similar kind of feel to it but it was a different (and specially composed) piece of music. You're far from the first to get them mixed up, though.