Good work, Al!
I feel I must defend 'my' zoo and Monkey Heights! The Diana monkeys and Macaques are always active and exploring their enclosures. . Monkey Heights looks attractive. There must be worse monkey houses around, surely!
I think you will find that different species behave exactly the same whatever surroundings/cage/enclosure type they are kept in. i.e. Dianas and some other Guenons, Macaques & Spider Monkeys are far more active than say, Colobus which as you know are often inactive for long periods while they digest food. Their surroundings have very little affect on their activity levels. Paignton's Diana pair were equally active in the old Monkey House, and the Colobus equally 'lazy'- it is innate behaviour for each species irrespective of enclosure quality.
Regarding Monkey Heights- I still think the outsides are a very strange design for a modern Monkey House. The more climbing facilities, the more the monkeys will use use them. Imagine those Dianas with a really large climbing area or better still, some trees to bounce around in- how even more spectacular would they be then?