Hi
That SNR Margin doesnt look to good Im afraid. :/
On traditional adsl anything below 10dB and you can start to see problems, below 6dB and thats when most users will start to see frequent disconnects.
Noise always is worst in the evenings because thats when more users are at home and online.
Ironically your Attenuation is quite good and indicates that your line should theoretically be able to support 2Mb.
and therefore your SNR Margin is lower than what I would normally expect to see.
Have you tried plugging your router/modem in at the master socket?
Theres also a test socket behind the master socket which you could try using to see if it improves your SNR Margin.
(Details and image half way down
Low SNR page. )
If when using the test socket your SNR Margin improves, then you would likely benefit by purchasing an NTE5 adsl faceplate.
As regards to contacting your ISP, I should image the likes of Talk Talk are well used to trying to fob users off if they can.
Contact them again clearly stating that your modem is showing that you have a very low SNR Margin, despite your attenuation showing that the line is capable of 2Mb speeds.
Ask if they would arrange to send a BT engineer out to check the quality of your phone line.
You could even request that they carry out a WOOSH test which will show them that you are reporting a low SNR Margin figure.
However, before you do this.. please carry out the master socket test, because when an engineer comes and if he finds that things are fine at the master socket then it does indicate that the problem is either with your equipment or internal wiring and may make a charge.
Therefore it would be good if you could also report to your ISP that you have tested from the master socket without any improvement.
Let us know how you go on with the master socket test and reporting it to your ISP.