I believe that pool and island enclosure is now the Asian short clawed otter enclosure. It was certainly very active with the otter family today. There was an old photo posted of it recently with a seal in it.
According to historic englands site the elephant house is the only listed building.
The sealion house was past its time and their new home at YWP is awesome. It’s a shame it didn’t become a new enclosure vs seating but it’s at least a tidy and well made space.
Edited to add the photo which shows the seal now otter enclosure which is the moated pool with island and half height fence courtesy of Skukuza.
Seal Enclosure - scanned photo 1990's - ZooChat