That is all.
Update: I had a response to my Twitter (that said, unsurprisingly, 'I hate Carphone Warehouse! They confuse intermal processes with customer services. Am very angry')
It appears they have a couple of customer services people who monitor Twitter for complaints ?. She got in touch, took my the complaint no, checked it out, and is authorising a credit note for us to purchase a new handset. Hoooray!
Well, perhaps I should save my 'hooray' until we've actually been to the shop and got the new phone, but it's a step in the right direction.