I am afraid they are very right, you are speaking about the wrong thing. The faut threshold is to do with sync nothing of speed e.g. if my line sync drops below 3312 I think then their is a problem.

But I currently download at around 800k but because it is not below 400k nothing can be done.

Not what i was told by BT and a bt engineer so at this time they are telling us different stories

It's download speed and not sync the thresholds relate to - that's why BT ask you to do at least 4 speed tests a day at different times from their approved speed test sites.

m8 connected at 2.5 which is SH*T in itself getting download speeds of .5 wooohooo