I had a rock solid 50 24/7 until I upgraded to 200 and was getting under 30. - since then no matter what speed I move to - i still get flaky service. I am on 70 now - this is the best time of the day for me to test because from 12 it will go down to nearly nothing until about 2am and then it will start to pick up.
http://www.speedtest.net/my-result/4842274154
That's my best effort as they say - 30 days notice is in, will replace with another BT line. I'd prefer to get this 24/7 on the other line as well.
http://www.speedtest.net/my-result/4842277116