Broadband connection dropping upto 20 times in a d...

Question

Having read others troubles and suggested solutions I thought I need to start my own thread to post the stats of the problem I have.
I'm staying with my inlaws and there broadband connection is atrocious, dropping the connection on a regular basis both day and night. Sometimes all is well for hours and others the link is up down up down not maintaining a connection for more than a few minutes at a time. This happens at random times but also almost guaranteed when an phone is in use (incoming, outgoing or sometimes even just if a receiver is lifted)
Below is what we've tried so far:
Original Thomson BT Home Hub (White) dropped both the internet and sometimes the hub would restart. I read this device had restarting issues so I think this was 2 separate issues. This has been replaced with a Belkin device. Belkin modem also dropped ADSL line (line and internet light on router both go out) but most of the time it is much quicker to reconnect.
Router is plugged in in upstairs office on an extension so I've tried moving it to the 1st BT socket in hallway. This is an old small square socket with no split facia or test port.
Replaced the RJ11 cable from filter to modem.
Replaced the ADSL filter modem is connected to.
Disconnected all other phones in household (there are no other devices eg fax)
Quiet line test performed at main socket no odd noises and only the very faintest of hiss (lower pitch than hiss but I can't describe) Almost inaudible anyhow.
With all of the above tried the line still dropped and so I've all but run out of ideas. What's the next course of action? Calling the call centre? I wanted to make sure our side was all in order before raising a fault ticket.
For ref the line has dropped twice while I was composing this post. Once with no apparent reason and once more while receiving an incoming call. Thanks for taking the time to read this I’ll post the stats from the router below.

Answer 1

Thanks for the reply I'll take a read of that.
It's taken this long to get back online and post the modem stats, sorry about the formatting.
System Date and Time    
Date/Time    March 19 2012 , 9 : 25 : 4
Version Info    
Runtime Code version     F5D7633-4Av1_UK_1.00.000
Boot Code Version        1.0.37-5.15
Hardware Version         V1.0J3
ADSL Modem Code Version  A2pB015c6
Serial Num               168-168-16888
Features    
Firewall    Enabled
NAT         Enabled
UPnP        Disabled
ADSL    
Type    
Status    No Defect
                  Downstream       Upstream
Data rate         2268             1108
Noise margin      19.1             6.6
Output power      18.4             12.6
Attenuation       45.0             23.8
From the Speedtest site
1. Best Effort Test: -provides background information.
Download Speed
1.78 Mbps
0 Kbps
2 Mbps
Max Achievable Speed
Download speedachieved during the test was - 1.78 Mbps
For your connection, the acceptable range of speeds is 800 Kbps-2 Mbps.
IP Profile for your line is - 2 Mbps
2. Upstream Test: -provides background information.
Upload Speed
966 Kbps
0 Kbps
832 Kbps
Max Achievable Speed
Upload speed achieved during the test was - 966Kbps
Additional Information:
Upstream Rate IP profile on your line is - 832 Kbps