It's true that the majority left the floor when the filming started and sat in the shadows, my reason for that is I didn't want anyone filming me in case my parents saw my eyes and I promise you more people didn't dance because of that than any other reason - so at least half the people who are on that film are, for want of a better word, divs, ask yourself, how many of those do you remember as regulars?
In 1976 when I first went, I wouldn't have gone near the front to dance, before the year was up I was dancing there, or anywhere else, it's just a case of getting used to it really, getting your confidence up.