Just thought I'd share a successful increase in broadband speed that you may want to also consider.
I have Sky unlimited broadband, and was only receiving somewhere between 1.6Mbit and 2.4Mbit download depending on which month I did the test. Calls to Sky resulted in them saying it's due to the distance to the exchange etc.
I have one BT master socket in the hall, and this is internally cabled to 2 sockets (one in the kitchen for the broadband router and another to a phone in another room), and an extension socket to the lounge for the Sky box. All end sockets have filters.
Since I'd recently got Sky Anytime setup using a LAN cable from my router I wondered if I needed the BT extension line to the Sky box anymore so I unplugged it and re-started my router. My broadband speed jumped to 5.7Mbits and stayed this way!
To test the theory I plugged back in the Sky box, and my speed dropped to less than 3Mbits, again unplugging and it jumps back to 5.7Mbits. I'm in a broadband slow-spot with most people registering under 2Mbits in this area - so I would seriously recommend unplugging all extensions you don't need and trying again.
Hope this helps.