Sync Speed has halved

Apologies for the long post but want to make sure I leave nothing out!
I am currently with Plusnet and I had a steady sync speed of 6080 kbps and a snr of 6.2 db ever since getting my new netgear dgnd3300v2 a couple of months ago. Previous to that I had the plusnet supplied thomson router and my stats were roughly the same but I had a lot of disconnections. A couple of weeks ago we had some light sockets replaced upstairs and ever since my sync has dropped to just over 2000 kbps and a snr of 26 db. I managed to get the speed up to 3072 kpbs by lowering my snr to 4.1 db. I am connected to the master socket (no test socket) via a filter with a phone connected also. I have one other phone attached via a filter to an extension. I have tried replacing filters, trying a different router and unplugging my phones but the stats remain the same. Plusnet told me to leave the router switched on 24/7 so they could monitor it but as yet have not given me any reason why this could have happened other than the electrician must have disturbed a wire, which he assures me he hasn't. I have tried the BT quiet line test but don't think there's noise on the line. I am at a complete loss and really don't know where to go from here. Any suggestions would be gratefully received. I have posted my router stats below .


System Up Time 21:21:24
Port Status TxPkts RxPkts Collisions Tx B/s Rx B/s Up Time
WAN PPPoA 1582901 3641289 0 1545 11482 21:14:17
LAN 10M/100M 183530 0 0 625 0 21:21:20
WLAN 11M/54M/300M 3719238 1651305 0 13161 2033 21:21:01

ADSL Link Downstream Upstream
Connection Speed 3072 kbps 448 kbps
Line Attenuation 44.0 db 26.5 db
Noise Margin 4.1 db 24.0 db

A couple of weeks ago we had some light sockets replaced upstairs

bog standard 240VAC light sockets, or some fancy low voltage DC / dimmed arrangement ?

Just your everyday bog standard ones.

Try turning off that light circuit at the fuse board and see if it has any effect.

There may be a slightly lose wire that is causing RF noise, and by removing power on circuit it improves. If it does then get electrician back, as this could spark and be cause for a fire in the future (rare but possible).

I already tried that I'm afraid. I also got the electrcian back yesterday and he checked all the wires for me, but there was nothing wrong electrically.