Peak period problems

Every afternoon at 4pm my throughput drops to 400k, rang BT up and they said there is no problem as it peak period only, like most ppl I work during the day and at nights it even hard to watch something on youtube, I know its not traffic shaping as FTP is also slow during this time, anyway, My question is has anyone else had these problems before and got them sorted? and if so HOW??
BTW my connection is usually around 4mb at off peak times

Bt are working on the issue it is getting better at times and then it gets worse,

thanks for the heads up m8, think Im in the worse at the minute, just hope it gets better soon