Just to let you guys know that after a bit of pushing, Google have finally given me the solution that I've requested. RMA the phone as a 16GB model, they'll send out a 16GB model when it comes back in stock in a couple of weeks (for those of you who missed out, that's when you need to start looking again!), and return through TNT. In other words, exactly the same method that Apple use with their advanced CRU replacements (for those of you who have had replacement Macs and boxed iPhones).
No refund on postage, but that's fine, considering that they said they don't mind me using this phone anyway.
Very happy. Now I can use this gorgeous device properly!