Re: Pull out...
Also replacing the old NTE5 Master socket with a vDSL Openreach one can help as well.
My ex girfield was a long way from the exchange (miles), and not yet FTTC enabled (old cabinet) and managed about 4Mbps at best, and was flaky.
I replaced the standard face plate (NTE5), with a Mk3 vDLS one, and it went up to 6Mbps, and was a lot more stable.
She later switched to FTTC once her cabinet was updated, and gets ~20Mbps through the same socket now (20 is what she paid for).
Just search for 'BT Openreach MK3' on Amazon/ebay etc.
Also if you don't use them, disconnect any extensions coming out of the master socket. My old house had two extensions, and as I used a wireless phone plugged directly into the master socket, they weren't needed, so I just pulled the wires out from the back of the little removable plate. I went from ~16Mpbs to 18Mpbs at the time.