Sudden regular disconnects on ADSL2+

[#1]

Things on my broadband have been pretty stable now for over 3/4 of a year since I got connected with Plusnet.
Over the past month I have started getting disconnected from the internet (or "losing sync")
I have changed nothing in my setup, there are no problems with my home network, I can connect to the TD-W8970 router just fine, but the TD-W8970 has been losing sync.
For the stable times my line stats have been something like
Sync speed up ~900kbit/s down ~1312kbit/s (this has varied, when i first connected it used to go as high as ~2000bit/s)
SNR margin up/down ~4.5-6dB
Line Attenuation ~68-69dB (down)
Using mapmyrun to get the main road route distance to my exchange (of course I have no way of knowing if this is the route taken but it was a guess at where it was going) the distance to the exchange is 4.1km
Since starting to get disconnected, I have found that turning off the router for ~30mins and turning it back on again can sometimes get me connected again, but it will usually become disconnected again, up to 4 times a day recently.
I am using no extension wiring, I am plugged in to the mastersocket, I have used 2 different filters, tried with the phone plugged in, without the phone plugged in, it has been happening in all situations. When I do get connected I get 1312kbit/s sync speed, snr margin of 6dB and line attenuation of ~70dB
I decided to play around with the settings on the router out of desperation. Usually, the modulation type is set to automatic and this automatically goes to ADSL2+. After first trying G.DMT (which I understand to be ADSL1) The line synced straight away and I have the following stats:
sync speed 900kbit/s up and 1888bit/s down
snr margin up/down: 5.8dB
line attenuation 31.5dB up 63.5dB down
Since changing the modulation type I have not yet had a disconnect, but I shall reply on here if I do (if I can get reconnected)
My question is really, why is this? And should I keep it this way? What is best? Could something have changed on the line to be causing so many disconnects in the first place before my messing around?

[#2]

G.DMT only uses the lower frequency half of the ADSL2+ spectrum, so it could be that there has been an increase in interference in the upper band or the modem-router has developed a fault.
You may be able to squeeze a bit more out of the line (possibly as much as 500kbps) by using ADSL2 (not 2+), as this doesn't use the higher frequencies and can make better use of the line than G.DMT.
With ADSL2, I get about 3Mbps at 7dB SNRM and 61.8dB attn. (4.53 km), with a max stable* rate of over 3.5Mbps (3dB SNRM).
Phil
* hold sync for at least 4 weeks - though doesn't occur often

[#3]

Hi PeeGee masterfunk,
There are various disconnections that have lasted for varied time periods in the past week (as seen in the graph below). This has caused your line to become chronically banded. Please raise a fault here: http://faults.plus.net so that our Faults team can investigate this and raise this to our suppliers if necessary.
<img src="http://community.plus.net/visualradius/generated/image14029264964233.png"/>
EDIT: Sorry about that masterfunk, my eyes must've tricked me into thinking the latest post was the original post.

[#4]

Quote from: Linn

Hi PeeGee, There are various disconnections that have lasted for varied time periods in the past week (as seen in the graph below). This has caused your line to become chronically banded. Please raise a fault here: http://faults.plus.net so that our Faults team can investigate this and raise this to our suppliers if necessary.

Linn,
Don't think that's my log - my modem-router is reporting over 183 hours of sync Prior to that, it was up for 76 hours
I have 5 IP changes logged this month - 5th, 6th, 9th (2) and 12th
Phil

[#5]

I don't think the DC team have had their coffee yet this morning!