I was also there...The lineup was absolutely stunning!!! The first day (Thursday) was punk: The Damned, The Clash and cannot recall the name of the third one.
For the next 3 days they played Rock. Besides Thin Lizzy, played: Elvis Costello, Ted Nugent, Aerosmith, Uriah Heep, Ian Gillan Band, ColosseumII (with Gary Moore and Don Airey ), Tyla Gang, The Sensational Alex Harvey Band. There were still others, whom I don't recall. But between Friday to Sunday was pouring rain and everybody was rolling in the mud. Even some musicians wore the rubber boots.