Thanks for the info, the Hippo complex was probably one of my favourite exhibits from my visit yesterday overall, along with Cheetah Rock, the penguins, and the enclosures along Lady Yule's Walk. I would say the Hippo House is still pretty great despite it's age, though maybe it would do better focusing on Common Hippos and having Pygmy Hippos just at London, although as I said it is great being able to see both types alongside each other.
I think ZooParc de Beauval have both, though I wonder if anywhere houses them pretty much together like they are at Whipsnade?