Just a quick update - thanks to all those that have emailed in - we'll be in touch as soon as we can start trials.
So far it seems BT may possibly have a bug in their order processing that means these orders just don't work. We are trying to get that fixed now. It does kind of suggest this will be a pretty unique offering though. So I'll update when we know more.
Update: BT a/c manager has confirmed: "I do have access to a Openreach specialists who can help us with the questions that are raised. He has informed me that the renumber for exporting is a current process then in theory should work." so we are not going mad, this should indeed work. Working with BT to get it fixed now.