Well, that is one brutally ugly enclosure. There are so many zoos that have large, grassy, naturalistic lion exhibits and some of them are actually too good because it can be extremely difficult to locate the big cats. Colchester allow their lions to lounge on wood on top of fake cement hills with nothing in sight but a few logs. One could debate the merits of the functionality of the exhibit but aesthetically it is simply awful. What is with the mock-rock backdrop in only one place? What is the point in that? Yikes.
It ought to be borne in mind that natural rock is not something Essex does. And I don't suppose the Lions bother much. But, yes, it is ugly, and if aesthetics are a massively important issue in an individual's appreciation of a zoo, then Colchester may well not be their ideal collection.
I think the rock is also a hot rock by that I mean has heating elements in it to warm the surface. when i was last there in November the lions were at the very back virtually out of site behind the rock mound, a few shrubs and more large logs or tree trunks would help a bit too.
I preferred the old enclosure it had self sown shrubs and change in levels and the lions always came close to the glass, here they are always well away. I know they are different lions so that may be the reason. As you say banham tiger, atypical Colchester exhibit, sadly they lack some one with an eye for landscaping their enclosures.