A Resolution of Speed Problems.

[#1]

The enclosed graph shows the results of numerous BT Speedtests made over a period of approximately 18 months when I have been able to increase the speed of my connection considerably.
We live in a rural situation some three miles from our telephone exchange and the first major increase in speed was the result of BT renewing some 10 telephone poles which were too short and did not meet today's Health and Safety Standards. It was decided to renew all the wire as well which amounted to some 600 yards as it was some 40 years old. Following this there was an immediate speed increase which tended to decrease slightly during the winter. We had a considerable amount of snow and high winds which may have affected the telephone line adversely.
Recently I read an interesting article in the Sunday Times about the BT iPlate and decided to purchase one. It is exceptionally easy to install - you take the faceplate off your BT Master Socket, slip in the iPlate and replace the original faceplate using  the two longer screws provided. This takes about 5 minutes and costs about £10.  Immediately the BT Speedtest results improved further as the graph shows and it will be interesting to see if there another uplift as the connection settles down.
I thought that other Plus Net users may find the foregoing useful as a means of  improving their connections.
Regards,
Davidhil.

[#2]

The effect of an iPlate is highly dependant on your internal extension wiring; could you describe that for us please?
And where is the router connected?

[#3]

Hi Bright Spark,
The Master Socket was situated by BT somewhat inconveniently in our loft when they rewired our telephone system  some years ago. The input telephone cable enters this and there are two output wires from this Socket one of which goes to the computer room, where it feeds via a BT Socket into  a Belkin Surge Protector. The output from the Surge Protector then goes into a filter which splits it, one half going to a Siemens Gigaset 5455 Base Station and the other half going to my computer which is an Apple iMac via a Voyager 107 Modem supplied by Plus Net. This Modem is located alongside the computer.  The Base Station has a total of three handsets connected to it, one in the computer room and the other two throughout the house. The other wire from the Master Socket goes firstly to a filter to which is connected a straightforward Binatone Caprice 600 handset located in the kitchen  which will still operate in the event of a mains electricity power failure.
I hope that the foregoing will be helpful.
Regards,
Davidhil.

[#4]

Thanks very much for the description.
Yes, that's complicated enough (and inconvenient enough) to make an iPlate well worth trying.
Glad it helped you.
It might be possible to get an even better result, but it would be quite difficult with your wiring. 
There are many people with much simpler setups that probably wouldn't benefit, or could get a better result with other simple DIY changes.