As I have posted, we are working on stuff with BT renumbering and number export (which is going quite well now actually), but in part of the process I got to understand the BT systems a bit better.
For amusement I checked, and the quite distinctive telephone number that we first had when we moved to Bracknell was in the free number pool. We have not had that number for over 20 years now. So, as part of my testing I had a play, renumbered on to a line, and exported to VoIP. It worked!
I think it is quite cool getting a really old phone number back. I found I could get my wife's old house number from when she was a kid, but she was not at all interested. Maybe it is just me. It is not really a "service" we can offer though, sorry.
Anyway, first and only call so far on that number:-