Unfortunately there are two extensions coming off the master socket. One is wired into the back of the faceplate I believe (when I take the faceplate off to expose the test socket there are two wires going into the faceplate). The other is simply plugged into the front of the master socket.

Reading that and your earlier description I'm a bit confused, but what is almost certain is that the plug-in extension will have a ring wire that needs blanking off for optimal ADSL.

I can't see white mentioned either, to be fair to cable universe it will always be way more expensive to buy cable by the meter as it takes a lot of time to measure out the cable and them wind it up, you also end up with wastage. I'm sure they would much rather sell you a box than have to measure it out.

Not sure about colour but when i was looking at prices in September the cheapest for cut length solid UTP cat5e were Cable Universe at 29p per metre and some Ebay sellers. Next best was Kenable with a 100m box for about £20.

As I said in the other post its only worth using shielded cable if the termination is handled correctly, so the shield is earthed. I'm not 100% sure what correctly is at the moment.

Sheilding should only be connected to earth at one end.

Ah right. Well in that case CAT5 seems to be unnecessary hassle/expense. I disconnected the ring wire at the master socket and all extensions a while back.

Another noddy question then - is 'standard' telephone extension wire usually twisted pair? I assume not just because of the fact you mention it at all.

A lot of the cheap phone wire isn't twisted pair. I'm still not too convinced about the stuff I bought from Maplin many years ago.

As regards the other wiring - often extensions go the long way around. In my case they run from the lounge to master bedroom then across the house and down to the office area. The idea is to run the best quality cable (phone or Cat5) by the most direct route. If your cable for adsl would follow the same path as the extension wiring then there might not be much to gain IF the extension is already in twisted pair. Arguably the number of twists in the different grades of cable may help or hinder.

The flying lead to the router could be picking up noise - they do tend to be long and rubbish.

The best way to estimate any improvement is to get router statistics from your normal location and compare them with using the BT test socket. You'll never get better than that! NB: If your router lead is poor that will effect the result at the test socket too.