Ahh-ha!

After more conversations with BT yesterday trying to figure out why they had closed the fault when the ADSL still wasn't working (when I had been previously told that the ADSL not working would definitely be fixed by BT, as it was them what "broke" it, and that I definitely did not need to contact my ISP).

Call Centre Monkey #1 (who put me on hold some five times during the conversation) kept telling me to contact my ISP about it. Every time I asked "So what's changed for the fault to be closed today when the phoneline has been working for the last five days?" he seemed to put me on hold, come back, then answer a different question, before each time telling me I had to get my ISP to fix the problem.
He eventually agreed that he'd get his supervisor to call me back, as she was supposed to have been dealing with the problem anyway (I spoke to her on Saturday).

Just as I had given up hope of her phoning back, she phoned back. She explained that the ADSL fault had indeed been reported to BT Wholesale (who provide ADSL to other ISPs who then resell it as their own), so I did not need to contact my ISP to report the fault.
However, because it was no longer a line fault, the existing BT fault had been closed, and if I wanted to track the ADSL status, I had to contact my ISP to find out what was happening, and BT Wholesale could provide them with updates (BT Wholesale obviously isn't allowed to speak to normal BT).

Well, that seemed to make sense, so I accepted that they closed the fault, and that they could close the new one. (I had to report a new fault to be able to talk to the call centre, as if it didn't think I had a fault on the line the automated system just kept telling me to sod off :)

So, I immediately contact my ISP to let them know. "Well," said the bloke at the other end of the line, "I've never heard of BT being able to report a fault to BT Wholesale before. ... Wait, have you ever actually connected using us? It says here your ADSL is due to be activated on the 17th."
"Ummm, ye-eees..."
"One moment..." [on hold for 30seconds]
"Ok, it looks like what happened is that BT had to replace the line, so they had to issue a cease & reprovide order on the ADSL, and you'll have to wait for it to activated again on the 17th."
"I see. BT suggested it would be fixed Friday...?"
"Well, depending on how busy they are, they are often able to activate the line ahead of schedule."
"Ok, thanks for your help!"

See now if someone at BT could simply have said, "we've had to replace your line and order a new ADSL activation on it", I'd have been (relatively) happy, but they never gave me an answer as straight forward as that! They have to send you 'round the houses with all sorts of meaningless gibberish that they make up as they go along.

Anyway.

It's working now! :)

At bloody last ;)