The key is to log it as a problem with the voice line, not as an internet problem. I know it sounds stupid, and it is, but they don't care that it's the same wire between you and the exchange. All they care about is who's paying them, and you're not paying BT for your internet connection.
When the tech comes out to me tomorrow I'll be telling him all about the crackly line but I'll make darned sure he sees my modem/router's DSL status page as well. I have no doubt he will be happy to investigate and fix everything that's wrong with the line.
EDIT
And, when you call, make sure you do it from a corded phone attached to the test socket inside your BT master. They ask you to do this to prove it's not equipment inside your home or extensions you have installed that are causing the problem. Doing it before they ask you to just makes the process of getting them to accept they need to send an engineer out a bit quicker.