Yeah, when we were on ADSL2+ over the copper line ours would go up and down all over the place to where the line would just go dead.
BT sent their engineers out to test our copper line and there was a hair line fracture in the outer casing of cables right where our pair was located, sadly there was no more free pairs available and they wasn't going to lay an additional cable just for one line.
So when it rained heavy our line would go bad, bad wind also caused issues too.
The really bad thing was most of the time when the line went dead, BT's tests showed it was dead and calculated it was an external fault, but when every their engineers came out to test it the line would start working again, but still bad.
The engineer did do some tests and there was a single wire that was broken between the hardware in chamber by our pole and the phone cabinet. They did say that they won't replace the whole cable or add a new additional one just for one line, which confirmed what BT told me on the phone.
That was why when we was able to get FTTP we got rid of the copper line fully, basically I terminated it in the BT80 box.
BT at the time was nice though they reduced the ADSL 2+ Broadband cost to about £5 p/m which was nice considering we was only getting 4 to 5 Mbps on a very good day to nothing when it was windy and raining.