24/02/2014
BT have finally confirmed that there are indeed exchanges with congested backhaul. They are not quite refusing to fix things yet, but indicating it will take some time, which is a big concern.
Any customers suffering congestion on BT 21CN backhaul lines can ask for a free more to TalkTalk's uncongested backhaul. It takes a week and has no charge. There is an outage of a few minutes, then it works the same as the BT 21CN service in almost all ways but gives slightly better control of line profiles and has no DLM.
Just talk to support or sales if you are fed up with BT dragging their heels here. I know this is not many customers (yet), but we need to address this issue with BT and it could take some time. We do not want any of our customers suffering.