Also, a few notes:
It could be a lot worse. At least your wiring doesn't appear to be filthy and someone appears to have used proper harness tape on some parts. Definitely could use a good going over and rectification of any issues though.
I'd repair the white wire's insulation with sealing heat shrink. Try to ensure the terminals your replace are good quality. They should be nickel or tin plated and of reasonable thickness. Cheap kits online are usually thin steel. Hi Temp made in USA kits are one of many good options. I prefer uninsulated terminals with the correct crimping tool, but waterproof insulated terminals are decent too.
The braided cable in pic 4 appears to have a discolored area which indicates it was rubbing on something. Braided cable is abrasive and really should be sheathed to prevent this. I'd look into this, as if it didn't cause the issue at hand, it will likely cause one in the future.
The red/white wire should be repaired as well, similar to above, with either a high quality uninsulated crimped butt connector with waterproof heatshrink over it, soldered and heatshrinked, or a waterproof crimped butt connector.
As a general strategy for this vehicle, you'll probably find that the areas where people don't look are where it may need attention. I mean this constructively, but companies such as Monarch often take what is essentially a farm truck and flip it to a more wealthy audience by transforming it (at least visually) into a more G-wagen like luxury SUVs. They do this primarily by painting and reupholstering them. Some go further, but it really varies, and the quality varies as well. Your truck looks really nice, but it's hard to know how well the electrical and mechanical has been sorted without a really detailed look.
The juxtaposition of the nice paint/upholstery and the very agricultural 200Tdi engine in this truck is interesting too. The 200Tdi is a fun little engine that I really enjoy, but it is a little engine (especially in a 110), and like nearly all old mechanical diesels, is loud and often smokey. Most owners who move into high-end Defender ownership without understanding that they were engineered for agricultural, rural, military, NGO, off-road, etc use where high-speeds are a low priority, are often disappointed when they don't fly down an American freeway at 80mph effortlessly. Hopefully it'll treat you well after this initial hiccup. They're a simple, easy to work on, all mechanical engine, with a nice sound. They can be very enjoyable if one values those attributes. If its agricultural nature proves impractical though, there are several engine swap options available that can transform the performance. Anyways, welcome to classic British car ownership! The classic Land Rover world is a particularly fun slice of it.