Hey Pitfigher,
Those are not ZB loaders, they are both styles of Bren. The one clamps to the magazine chest as pictured, and the other stores in the front of the chest as you can see in Richards photo as well. Granted they look the same, but you are correct in that the ZB loaders will not fit Bren mags. I have a ZB loader for my ZB and if I recall I bought it assuming it was for the Bren since I couldn't tell the difference at the time. I wish the loaders were as common as the ZB loaders, but they indeed took quite a while to find.
The sight is a fixed line sight and what looks to be a binocular case is the case for it with a wooden insert that the sight goes into. Not pictured is the light box setup and stake that is shared with the Vickers. The sight slides into the front dovetail in a MK1 often referred to as a "double dovetail". That was fairly quickly eliminated since it's only purpose was this sight and the dream of the No.32 scope mount that would fit into the front dovetail that never materialized. Machining this beast was complicated enough and later marks got rid of the dovetails altogether.
The chest is unfortunately Canadian, so technically not correct for this Enfield, but so far it's the nicest one I could find. I've seen a lot of British chests, but they all so far, have not been that nice or there was a shipping issue on the nice one's I did find.
I had always assumed a Bren would be out of reach since prices when they come up are very high, but on a sheer quirk of luck at an auction, there were few bidders I and stumbled into it. I'm not sure I've ever seen another early Bren like this come up for sale publicly? The gun came out of a museum, as did the sight in a separate lot.
You guys need some cleaning rods in those lids! Same as the Vickers IIRC? Without the Bren gun saga, I wouldn't have gone half this far, but I think I am only missing one or two items from memory? I think only the MG34 is worse for accessories?