Going sslllloooooooooooooooooooooooooooowww again

[#1]

My broadband speed has been a lot better since BT eventually decided that there was a problem with the phone line (the cable was split and letting water in and was only connected by a few wires due to it being up there since the year dot), since then I've been getting 1.6 meg all day and every day, but for the last 2-3 weeks it never gets above 970, can anyone shed any light on this?

[#2]

The first question is what are the stats from your router - speed, noise margin, attenuation - this tells you how to get them http://www.kitz.co.uk/adsl/frogstats.php and then what does this say https://portal.plus.net/my.html?action=data_transfer_speed

[#3]

Checked the stats,
down speed is 1376, up is 448
Noise is 12db down, 7db up
Attenuation is 61 down, 63 up.
What does this all mean?

[#4]

Basically with a sync speed of 1376kbps the IPprofile will be 1000kbps which means that the speed tests are about right.
What I think happened was that something caused the default noise margin to increase from 6dB to 12dB which will have knocked your sync speed down quite a bit.
Would it be correct to assume that nothing has been changed in your house - you are still using the same socket etc.
Do you have a master socket as shown in this picture. If so can you connect to the test socket and report the stats. All this does is rule out any internal wiring problems but given your attenuation I suspect that isn't the cause.
The thing we really need to bottom out is why/when your noise margin was changed. I don't think you can get this directly but if you raise a ticket to Plusnet asking them to give the times and changes in the IPProfile over the last month this will be a very good pointer.
Just to add - your upstream noise margin is still far too low and the upstream attenuation is far too high which indicates a problem with the line. If you pick up the phone (corded not cordless) and dial 17070 then option 2 - is the line totally silent. Try it with and without the router connected using the test socket

[#5]

Oldjim has given some very good advice there, let us know if you need anything else.