That's Paul Champman playing the Non Reverse Firebird - so after Michael Schenker's departure, not the band's high point, though that wouldn't have anything to do with Chapman. Pete Way was an alcoholic so yeah the open fly on his trousers isn't a big surprise, from what I understand his behavior was at least part of why Schenker left the band as he was a rather unpleasant drunk. For a short season UFO was utterly brilliant, the inclusion of Paul Raymond on keys and guitar added to their sound immensely and Schenker's playing was huge, as a teenager I thought him to be worlds better than Jimmy Page, Clapton, etc. I saw them once at the U of W with Blue Oyster Cult just before Schenker left, he was very good that night, Pete, being Pete, pushed his Marshall stack over with his Thunderbird when they finished their set - not his best night on the bass.