I've spoken to BT this morning, and it appears that the fault may not have been reported until Sunday (after I reported it on Saturday – not sure what's happening there). They have no idea when it will be fixed … although the guy promises to call me this afternoon once he has looked into it.
As it stands, an engineer is down for Thursday (3rd). I have pointed out that it's multiple people who have no service (the people I know of in our block plus there are friends around the area that are also off).
Sadly, my initial optimism that the service level would be anything greater than “worst possible” seems to have lapsed. He did confirm that it is a BT problem though.
When (if) he calls back I will update.