Well today I cancelled my order with Oculus and ordered from Amazon.co.uk. It should be arriving on Friday!
The only way to cancel with Oculus is, oddly, to send a support ticket. So that's been sent, notifying them of the cancellation, but I haven't had a response from them yet, and my order details remain unchanged. Felt slightly foolhardy reordering elsewhere when the cancellation of my initial order has not yet been acknowledged! But I'm sure it'll be fine!
I place my order with Oculus on July 28, receive an email on Aug 4 that my order is ready for UPS to pick up, along with a tracking number.
Guess I got lucky or they are catching up with the orders they got.