@PAT this is the oldest map i kept. The basic layout of the Zoo has changed very little since its inception, with the most significant change being the carve out of the area in the lower right corner to become River Safari.
The biggest changes between the 1980s and 1990s were the additions of Treetops Trail (prior to that the area had standalone exhibits for Asian small clawed otters, Humboldt penguins and lemurs); Primate Kingdom (prior to that the area had a few primate cages); and Children's World (prior to that the area was barren land).
@DavidBrown the Zoo had 4 gorillas (2 from Bristol Zoo and 2 from Monaco) between 1982 and 1984. All succumbed to a tropical soil disease. They were housed in what is now the Chimpanzee and Mandrill exhibits. Another 2 gorillas were acquired from Dublin Zoo in 1992 and displayed in a semi-indoor enclosure used for animals on short loan or new arrivals (labelled as "SPH" on the map). Sadly one died of the same disease within six months. The remaining gorilla was returned to Dublin zoo in 1993.