Probably go for the steelbook, though it's a bit underwhelming. £69.99 for Deluxe really is near the absolute limit to what I would pay for a single movie. 5CM is more appealing anyways, so hope that one turns up alright.
Not too bothered about the UE as I didn't like the film quite as much as YN and don't have a 4K player, but the CE is poor compared to the Promare one which went for the same EB price. And a bloomin' steelbook! I have zero steelbooks in my collection, but having said that I'll probably still go for it for the DVD to send to my little sister when I send her the Shinkai films.