I really like Whipsnade but I have never liked their sealion accommodation or the performance aspect. Other than that they are mostly excellent.
I visited Heythrop for the first time yesterday, thoroughly enjoyed it. Great training and working relationships between people and animals. Nice to see flighted Pelicans (pair of Pink-backed ex Christopher Marler), sizeable breeding group of Red Kangaroos, Pygmy Hippos. Humboldt's Penguin breeding colony now have an enclosure and pool as good as I have seen anywhere.
I too visited yesterday and am happy to report the new penguin accommodation is now excellent and their breeding record is also very good.