I realise that I'm replying to the old bit of this thread, but it might help still...
Isn't there an obligation on Openreach (and/or BT Wholesale) to have the correct address that the phone line is physically provisioned for?
Certainly they are required to use location information for emergency calls - to both supply that information to the emergency service, and to choose which service will take the call (eg, which county police force).
If they have this address information wrong, surely they are failing to honour that commitment, *and* potentially putting your family at risk! Well - it's an angle to pursue the change with anyway
BT Wholesale's 999 product description