I got a bit bored and nosy, so I took a peek at the progress at the BT forums. Good to see that you've got responses, so that's progress.
DanielS said:
Providing it's available to you, we should be able to change the upstream to uncapped. However; we will have to change your onto ADSL2+.
This is confusing me a bit, since it seems like it is almost implying that you need to move from ADSL Max (to 21CN) rather than it just being the case where you are on 21CN and they just need to uncap the upstream and enable ADSL2/2+ on your line. I could be wrong, but I know BTW 21CN connectivity from the DSLAM perspective allows for capping to 448 kbps on the upstream since it was and maybe still is the standard for Plusnet provisions (I know the OP is with BT, but just for example), and I don't see any technical limitation to disabling certain modulation modes.
To me, it seems a bit counter-intuitive to provision someone on ADSL Max (20CN, essentially legacy connectivity and backhaul) where ADSL2+ enabled 21CN connectivity is available. Of course, the excuse of low estimates could be used, but to me all this is just not adding up.
Perhaps someone here can shed some light on this? I could be wrong completely ... maybe I am just going insane.
Anyway, sorry for stealing the spotlight and essentially hijacking the thread for my own curiosity.