As of 8:30am this morning, 'Delayed' on the UKMail site with no estimated ETA. So fired up a chat session with the Apple Store...
Q: If I give in to impatience and buy an ATV in-store, can I return the one UKMail are delivering to my local Apple Store unopened for refund?
A: Not to an Apple Store, but we can recall it from UKMail so it won't be delivered and you'll be refunded when we get it back.
Which sounded like a decent plan to make sure I'd get one today. Except Sod's Law struck, and UKMail updated to 'Out for Delivery' moments after I ended the chat with Apple. So now not sure if UKMail will actually deliver today / if Apple's recall instruction reached them on time to stop them / or whatever, and not dropping past the Apple Store to pick one up there until I know the in-transit package has been stopped or delivered. Another day potentially without New Toy.
Damn my impatience, coming back to bite me. ¬_¬