OP here. After a lot of agonising we used a professional pet-relocation company for our big dog, and honestly it was worth it — they handled the crate training, the paperwork, and the cargo booking, and he arrived calm. Expensive, but the expertise removed the terror.
The vet says my dog is too big for the cabin, so it's cargo or a very expensive pet-relocation service, and the thought of him alone in the hold terrifies me. How did you weigh cabin vs cargo vs a specialist courier, and — honestly — how did your pet actually cope with the option you chose?