My first visit to London zoo was in the mid 1980's, I don't remember a great deal:
Cotton terraces: all houses were accessible to public, and you could walk down the steps into the antelope houses under the path above (now the hunting dog/ wild pig indoor areas), and see all the species not currently given the outdoor paddock that day as the zoo had many on rotation sharing one outdoor yard on different days. The current tapir area was split for lowland tapirs, and vicunas/ llama & Alpaca (depending on the day). The other side of this house had a moated camel area, and the back paddock (still used for Arabian gazelle) was visible through the bars and held przewalski horse and zebra. The giraffes had a third less space due to the camel area and dividing moats. The okapi were next to the giraffes and shared the house. The rear area bookending the horse enclosure held anoa. The current okapi area was split like the llama/tapir area and typically held gaur and American Bison, both breeding when I visited. I remember sizeable numbers of blackbuck, bongo, Roan antelope, addax, greater kudu, and oryx in the lower houses.
Clore: The meerkat area before this still has canadian beavers, the roundhouse still had surplus orang utans, and the otters' old enclosure by the insect house had praire dogs behind it. There were tree kangaroos, galagos, echidnas, tasmanian devils, fennec foxes, margay, Brown Kiwis, and armadillos in the actual clore. Red ruffed lemurs were in the large open air primate space by the black rats. Wombats had the outside space later made into a marmoset enclosure. Parma wallabies lived in the small triangular area later used for mara. Many Brush-tailed porcupines had the bizarre moated complex where they appeared to be able to swim in the moat via access holes underneath the compartments. Three tree shrew species were present.
There were still many crane and goose paddocks on the North Bank, and some tropical birds in the Snowdon, possibly touracos.
The bears had just left the mappins, but there were still herds of Mouflon, some Bighorn and barbary sheep, many Wild boars and the long pool still there in the current bear area held brown and possibly white pelicans.
The southern aviary where the Komodo dragons are now housed had gannets and some of the black-footed penguins.
The stork and ostrich house had long 'runs' on the west side, housing single-wattled and bennett's cassowary, giant tortoise, giant anteater, ostrich, pudu and possibly emu.
The current hippo pool had californian sealions, with weaned young in the old seal pool by the children's zoo.
The last set of Asian elephants had just arrived, Layang-Layang (I forget her current name) was in the animals in action ampitheatre and can't have been more than chest height on her keeper. The hippos were in the pool in the elephant house. There were two adult white rhinoceros.
The old children's zoo had a larger reindeer and mara enclosure where the main pet building is now, plus a nocturnal house with aardvarks, springhares and douracoulis, possibly all sharing one set of enclosures.
The current australia (former camel) house was a row of aviaries housing curlews, pheasants, vulturine guineafowl and possibly some pigeon species.
There was a red panda enclosure by the elephant moat, as well as a circular, open-air pool for cormorants. Orange-rumped agoutis lived in the bottom of the elephant moat.
The cat terraces were very similar, only there were jaguars, leopards, a puma, possibly cheetahs, and african lions. There may have been servals too.
The grey foxes had just left but were still in the brochure, and the 'meet the monkeys'/ anteater area was a very large 'wolf wood', as immortalised in 'Withnail and I'.
There was an extra aviary block for corvids/tropical softbills near to the parrot house, the building still stands today but I think it is a staff parking area now and visitors no longer have access there.
Chia chia and Ching ching(?) the giant pandas were in what is the current gibbon cage, I also remember a 1.1 gorillas in the sobell with a very young infant, also Mandrill, capuchin monkeys, squirrel monkeys, King colobus and pig-tailed macaques.
I remember bateleur eagles and caracara in the old bird of prey aviaries. I also remember quetzal and pygmy falcon in the bird house, though this could have been seven or eight years after the first visit. The old Great Indian hornbill was in an indoor enclosure in this house.