I couldn't bare the lower than dialup speeds any longer so on Monday I called support & requested an engineer asap. The chap asked me to call back in 40m to get my appointment. When I called it had been booked for the next day which I was pleased at. Engineer was here around 1 1/2 hours & in that time I watched my line pass one test after another leading me to fear a charge. Luckily I still had my new pc in the living room & he asked me to run a speed test. As expected it was showing 3kb/s so he asked me to run the BT test so he could confirm my profile. When he saw it was 135k he rang someone to request my profile be reset because it was to low & whoever he spoke to said my like was set to a 2000k profile. After running another BT test & some debate over the phone including the line (sounds like another 21cn disaster) it was decided something was borked & not communicating with other gear. He said something probably needed rebuilding & spoke to the person on the phone again. Then he requested I ran a speed test & boom I had boradband speeds again. I can only assume I was switched over to anther piece of kit. He then left saying he would try & tweak some more speed out for me. My line dropped twice 15m apart & has been synced ever since. I'm assuming he was doing something either at the cabinet or the exchange for those two drops. Whatever was done did nothing to increase my speed. Before the issue I was synced at 5,920 on a 5000k profile getting 4.9Mbit aka 620kb/s speeds. Now I'm synced at 4,288 on a 3500k profile getting 3.2Mbit aka 420kb/s speeds. Looking at my stats I'm thinking my lower sync is because my snr is up at 15dB compared to 9db before the issue. It used to be at 6dB but BT raised it for some reason only they know. I may call Enta & request my snr be reset now I'm on new gear not faulty [censored].
At least I know my line is in good condition & I'm 100m away from my cabinet. Which is temping me to switch to FTTC
And the BT guy confirmed what I already knew that 21cn is a disaster. My connection was rock solid from switching to adsl up until 21cn then it's been crazy.