The majority of the clouded leopards at Howletts are housed in a complex of tall cages just north of the original first set of tiger paddocks. These used to be way more inaccessible to the public before the new land was acquired. This area has held marbled cats, snow leopards and servals at various points. A path runs adjacent to the taller cages but trees and climbing plants mostly obscure the leopards from the public, leaving one, large, display cage at the front of the complex. There are live shrubs and trees both inside and overhanging the enclosures, and many creeping plants along the wire. The whole area is suitably overgrown.
I think the aspinall's trick has been to work very closely with individual leopards, and as a result generally have had calmer animals whose individual personalities were well-observed by staff before any introduction was attempted. They also seemed for a while to introduce pairs while still young, to create some familiarity before sexual maturity. I speculate here but there are plenty of photos and accounts of keepers 'playing' with individuals of this species, so it could well be that a few animals hand-reared early on went on to produce cubs which were, along with their parents, consequently far less stressed in a captive environment and less likely to kill mates on introduction. Sounds paradoxical but it could be. There are occasions where hand-rearing produces perfect parents and very calm, manageable animals.
I don't really know what the policy is these days regarding keeper interactions with the howletts animals, but the site is not particularly sheltered from the visiting public, at least in terms of proximity and noise, although visually there must be an element of security if the cats are aware that the planted screens/enclosure height means they can watch visitors all day without being noticed.
Port Lympne has often had a few of the Howlett's animals, I assume these to be non-breeding, possibly elderly animals, and they tend to be located in the woods by the older guenon and colobus cages.