After hearing all of your whining, I thought I would give an idea of things from my point of view.
I'm unfortunate enough to be sitting in my business tech support chair at BT now. I've had a lot of calls regarding our inability to handle DCC traffic across our network. I've raised the issue as a major service fault and it has been recognised as an error on our servers.
Unfortunately it's not as simple as diagnosing the fault and pressing a big 'Repair' button, therefore fixing it. Whining at tech support agents won't resolve the issue. It's with BT Wholesale and they are repairing it as we speak.
Also, you won't get through to a British agent just by asking. Our residential helpdesks are based in Bangladesh. Our business support is based in Britain.
As mentioned before, don't mess about with your settings for a quick fix. Changing the port you connect on won't work, and neither will port forwarding. The problem is on our end of the system.