While I was googling to see if there is a new NGA Enquiry process I cam across this on the BT OpenReach portal ... but obviously its for partners online (requires ID).
Providers have access to more information since they have the relationships with the public and are thus the ideal conduit. The fact that very few bother to help says a lot.
Its a bit like getting in touch with Kellogs when your local Co-Op was out of stock of CornFlakes