Since the BBC have decided against re-broadcasting the Top of the Pops of 31 march 1977, PattifrorPM has kindly sent me a copy of Legs & Co's performance from that show: dancing to David Soul's Going In With My Eyes Open.
Update: Whoops! Looks like I spoke too soon: the Beeb is scheduled to show this episode after all. Thanks to everyone who was paying attention, even when I wasn't.
Thanks once again, PattiforPM.