problems since being LLU'd

I've been with TalkTalk for just over 12 months and since my exchange (Hawarden) was unbundled in April I've had nothing but problems with my broadband connection so I'm hoping someone out there can help me.
Since April my connection will drop after several hours and below is a snapshot of my Router ( Safecom SART2-4112) stats from 25th August around 4.50pm:

Connection Status Connected
Us Rate (Kbps) 446
Ds Rate (Kbps) 2931
US Margin 13
DS Margin 2147483647
Trained Modulation ADSL2
LOS Errors 0
DS Line Attenuation 57
US Line Attenuation 34
Peak Cell Rate 1051 cells per sec
CRC Rx Fast 0
CRC Tx Fast 0
CRC Rx Interleaved 2877
CRC Tx Interleaved 0
Path Mode Fast Path

I live around 3.5 km from the exchange and usually I can get about 2.1mb download speeds, I only use my broadband for surfing and emails and I'm not a heavy user. I've done all the usual checks re internal wiring and my router is plugged directly into the master socket. As said earlier the problems have occured since my exchange was unbundled in April and despite numerous calls to TalkTalk technical Support they have been of little use. They claim they cannot access my line to view the problem which I find strange. I was on a 9db SNR but requested this be increased to 12db a few weeks ago in the hope the broadband would hold but despite them setting my SNR to 12db the line keeps dropping (even more so when night falls)
has anyone got any idea what could be the problem(s)?

Any advice would be welcomed

Graham

Try forcing your router to sync in g.dmt mode (ADSL1). At the moment it is in ADSL2 mode which is not ideal given your attenuation. I would also try another modem to see how that goes.