I ordered the 8Gb on 9th July but changed my mind the very same day and put in a change of order notice for the 16Gb. I got no reply so put in a cancellation request with a view to reordering the 16Gb. Still no reply but I assumed (ha!) it'd be cancelled because I asked them to cancel.
I got a tracking number Tuesday and rang Google Play yesterday where I spent SEVENTY minutes on hold to be told by a pleasant but slow American lady called Nataaaaasha that if I wanted to exchange it for the 16Gb I'd have to "take it my shipping company and refuse delivery and they'll ref......<click>"
I'll probably keep the 8Gb and hope USB-OTG either comes via an update or is available via rooting.