SNR Margin Too Low?

[#1]

After some problems a few months ago with frequent disconnections, my broadband has been pretty rock solid since an engineer found a problem with external cabling in the street. Today, that's changed with multpile disconnects overnight, then it's been mostly ok through the afternoon, but just dropped again when the phone rang. My net and phones are separated at the main socket with an ADSL faceplate. But I know that incoming calls can cause error spikes. Looking at router stats, after a long period of stability, my guess is the exchange is automatically seeing if it can squeeze the pips out of my connection. From router:
"xDSL linestate up (ITU-T G.992.5; downstream: 15897 kbit/s, upstream: 440 kbit/s; output Power Down: 20.0 dBm, Up: 12.0 dBm; line Attenuation Down: 26.0 dB, Up: 14.5 dB; snr Margin Down: 3.0 dB"
SNR Margin of 3dB instead of 6dB (which I usually had) doesn't leave much scope for errors, I guess. Will the exchange automatically up the SNR to 6dB if connection drops persist, or does it have to be requested?

[#2]

I forgot it's a ghost town here at the weekend.
Oh well, not an SNR Margin problem it seems. My SNR Margin has gone back to 6db and still getting lot of disconnections. They did great this time, three months since the last line fault. As usual, and same as last time, the BT fault checker reports no fault on line. The whole street's lines were knackered last time and the fault checker said all was ok. 
If someone from PlusNet reads this on Monday, should I ring BT (who supply my phone line) or raise a ticket and wait a week for PlusNet faults team to get around to doing it?

[#3]

if when you dial 17070 option 2 the line is noisy report it to BT (don't mention broadband) otherwise raise a fault at https://faults.plus.net

[#4]

Your line is disconnecting a lot:

The advice from Oldjim is the best course of action.

[#5]

BT's line checker reports no fault  ::), but I rang and spoke to one of their advisors in India and seems the exchange has a fault reporting on the line. They said it'll be fixed within a week. I either got temporarily lucky, or someone did something a lot quicker than that, cos my connection has been up 11 hours now. Longest for days.