I'm so going to have to call back again ¬_¬
"A Representative on 156 for pay monthly or 450 option 2 for payg will be pleased to run a diagnostic in order to resolve this problem."
MY ARSE THEY WILL!
"If as you state, your handset is not being recognised by the Orange network, the issue will need to be referred through to Technical Support for a resolution for you."
I've asked. And asked. AND ASKED
"Should there be any problems with resolving this by phone call to them, then there is a third level of expertise which can be referred to."
Asking for that is going to be exciting
Still, armed with quotes from the lovely people at email support, I'll call tomorrow during office hours and see where it gets me. I've rarely had problems navigating the Orange machine in order to get what I want, but this has been a real challenge! Thanks to you all for your advice and discussion thus far.