I would certainly have a word with someone at BT. I had to be a bit pushy to get them to sort out the problems here, but since they did that, it's been flawless. I use Pipex as the ISP - good speed, reliable, and almost no customer service. I know several folk who are on AOL and have all kinds or trouble - yet still insist they want to stay with AOL. Very odd.
BT aren't bad per se - it's just like any large outfit - you get good and bad experiences. Bad ones need strong reaction, and they get fixed.
There used to be a "line test" number, that would test the line and phone back to tell you your line length - as I recall, it was 19090 then 3 1 2. It stopped working a year or two back.