I watched them demolishing the old dikdik enclosure on Monday. The workforce was man on a stepladder with a crowbar and another with a sledgehammer.
That's the way to do it! It's George Mottershead's old philosophy: build it cheaply, knock it down and rebuild better. Obviously you need a bigger investment for bigger species (orangs and sun bears spring to mind) but I admire the way Colchester is renewing its exhibits.