I've been there. Its quite scary because in one bit of the park your walking down a path and theres even a cage above your head with monkeys in. Imagine if one decided to pooh.
I love driving through the monkey bit in longleat. One pregnant monkey was really randy and jumped on our car and tryed ripping the rubbers bits off and the windscreen wipers and then she sat on the bonnet and ate a banana which seemed to last for hours.