Demon slow or unreliable?

I'm not sure if this is an ISP problem or something else, but lets go on.

I was using another discussion forum and getting lots of "Timed out" messages, so I ran speed tests.
bbMax says 2055 kb
ZDNet says 1000 kb
ThinkBroadband says 980 kb
I did run them one after the other - not all at once (!!!)

Question: Does anyone have any suggestions why I would get such different results so close together? I've had similar effects before.

Question: Can anyone offer an explanation for a connection with a reported speed of 1 MB to 2 MB (nominal 8 MB) that times out when I try to use Hotmail, Yahoo mail, etc.?

Could you post your router stats (sync rate, attenuation, SNR margin up and down as well as any error stats you can find, HEC, CRC, FEC etc.). See http://kitz.co.uk/adsl/frogstats.php

The router is a Zoom X5v in case that matters.
When I powered on this evening there was no Internet at all so I restarted the router. That often fixes that problem.

SNR down varying quite rapidly between 6.9 and 10.7
SNR up 14 and constant
Attenuation 25.9 down and 17.5 up

In the 1 hour 45 since the last restart:
Errored seconds 1 down 0 up
Loss of signal 1 down 1 up
Loss of frame 0 down 0 up
CRC errors 0 down 0 up
Data rate 7520 down 896 up
other errors all 0

"Speedtest.net" 5.45 / 0.75
"Thinkbroadband" 1.9 / 0.7
"Speedtest.bbmax" 3.94 / 0.7
It's a good day ...

You need to find out why the downstream noise margin is fluctuating. It does vary normally but gradually usually. Any local sources of radio interference? Sky box, microwave etc.

Is all your kit filtered? Do you get the same stats from the test socket within modernish BT master sockets? - that might rule in/out your home phone wiring.

Might be worth using RouterStats to see if a pattern emerges.

http://www.vwlowen.co.uk/internet/files.htm

This needed a bit of negotiation with family members to take out the Internet and phone connections.

RouterStats didn't work because my router isn't the same make as the one it is written for. It just showed a blank page.

We don't have a Sky box. We have a microwave but we weren't using it. We have a Skype phone which uses radio. I can't think of anything else. The TV was not on last time but it is now.

As I did the internal extension wiring myself that is a good place to start, although making a phone call didn't affect the results.

We have a BT master socket with a combined phone and Internet face plate. With that removed and the router plugged into the socket itself the results were the same as before.

At the moment the router is saying it has a downstream date rate of 7488 kbps. Speedtest says 5.46 Mbps, Thinkbroadband says 3782 kbps and Namesco says 5779.

One other thing I forgot to mention is the phone lines around here are underground, except for the final connection to the house, which is overhead and swinging in the wind.