Announced in White Dwarf 121 (Jan 90) to go with the Waaargh! the Orks book, they were released a couple of months later. The parts are shown in the 1991 catalogue here.
Box scans courtesy of Tony Mansfield.
RTB13 Space Orks - Box Art
RTB13 Space Orks - Box Side A
RTB13 Space Orks - Box Side B
RTB13 Space Orks - Box Side C