I remember seeing this on TV at the time - the second TBird player is a kid from the audience which Overend just pulled out and handed an unplugged instrument.
The British Lions were the Mott the Hoople remnants' last attempt - after the short-lived Mott - to leave the shadow of Ian Hunter behind. John Fiddler was initially a strange choice for a band as visually oriented as Mott - glasses, beard, slightly overweight -, but he morphed quickly into what you see in the vid. However, in the Punk/New Wave deluge of the time, their cause was a lost one. Strange that they had a full 45 minute live TV show awarded to them as neither Mott the Hoople nor Mott had amounted to much in Germany.