The BT Retail complaints procedure can be downloaded here: <<Link>> (PDF document)
Though once the BTCare Team (Mods) have responded and offered you their support and help they will be able to solve your broadband fault.
BT Care Team (Mods) are a BT UK Based specialist team who have a good reputation for solving customer problems.
Just remember this is just one customer out of >6 million. The happy ones would not even know this forum existed.
Check out other ISP's forums before you make a decision.
I'd love to know what the conclusion of all this was. I'm a new BT broadband customer and reading this does not fill me with a warm feeling...
Vintagemum has never visited the forum since last post in 9/2013 so reasonable to assume fixed