I will explain what peaked my interest on this.

I have a new Infinity install and everything was working fine except BT Vision which upon completion of viewing a programmed resulted in the QoS reasserting my old ADSL2+ IP profile instead of the Infinity one.

I went around in circles with India tech. I thought it had finally got understood. The next day, I find my upload speed reduced and interleaving up. I then get a call saying they have stablised my line!! I was furious. There was no instability. So I was wondering if they changed my Openreach DLM setting from Standard to Stable....or if they were doing line tests which just triggered an interleave up-level.

Either way, I am still struggling to get the Vision QoS corrected (contacted BT forum moderators now)...and I am not sure if there is anything to "undo" from BT's so-called techies in the India call centre.

Not disbelieving . Just aware, as I'm sure you are, of the infinite capacity of BT semi-techies, and also tech authors, to cock up things and documentation.

In reply to a post by yarwell:

Are you sure the order-time option for ISPs using WBC/WBMC works for FTTC?

The options are presented the same way, it's just a parameter like the speed / elevated best efforts etc. It all ends up as XML I guess.

The DLM option for Fibre based WBC will have to be applied to the Openreach settings as there isn't any other DLM, for ADSL WBC it'll apply to the DSLAM.

Edit: If you only believe things you see yourself, try page p118 here

As you can see from this document, all BTW orders are processed with a stability option set to "Standard" by default.