In reply to a post by alwall:

In reply to a post by anilvij:

Brown was on 2 and green was on 5, and I just checked the positions of the wires upstairs, its the same; with the addition of the ringer wire on 3, which I have removed. So now upstairs and downstairs is the same.

So were Blue/White , White/Blue originally connected? If so to what?

Sorry for the confusion... Brown shared 2 with Blue/White and Green shared 5 with White/Blue

In reply to a post by GeeTee:

OK well if brown and green were on 2 and 5 then there must be or have been another extension connected - could be a plain socket, burglar alarm, external ringer, flashing light etc.

For testing purposes I would first disconnect the blues from the faceplate so nothing is attached to it, then put the faceplate back in the master and see what the router syncs up at. If it is still low then it is the faceplate itself that has a problem. If it remains up near 2Mbps then it is the extension wiring to the socket upstairs that is the problem.

Removing the blue wires brings the speed to exactly what it is out of the test socket. The problem then, is the extension. What to do!

OK - so what is plugged in to the extension socket?

And are you connecting whatever it is via a micro-filter?

Something is introducing noise on that extension wiring - it could be the extension socket itself going out, whatever is plugged into it, or even something inducing noise on the wiring - wall wart power adaptors are common culprits, along with power saving light bulbs.

I'd also recommend you invest a couple of quid in a proper IDC connection tool - that way you can be sure the connections you are making to the faceplate are fully home and sound.

e.g.
http://www.amazon.co.uk/Solwise-Plastic-IDC-insertio...

http://www.amazon.co.uk/KRONE-Type-Punch-Telephone-I...

http://www.amazon.co.uk/Draper-40417-Punch-Down-Tool...

Hmm. Jiggling around with the two wires for a bit, making sure they were in as much as possible, seems to have done the trick. I now have my 2mb thank god. Sky promises me it will rise to over 3 in the next few days; fingers crossed.

Thank you so much for your help everyone. I feel like I've wasted your time! But at least I understand how all the connections work now.

Happy to help and glad you got it sorted. Once you understand how that spaghetti is supposed to be connected it suddenly seems very simple

Well spotted!