To clarify the point, undoing the two screws and removing the master socket faceplate will reveal the BT test socket which is where BT's responsibility ends. In your hand now is the start of the extension wiring which is now disconnected totally form the circuit. This wiring you can fiddle with to your hearts content (well, within limits).
The 54Mbs and 100Mbs you mention are not broadband speeds. Those refer to your local network speed, ie, the connection speed between several networked Pc's or Router and PC. Not the router and ISP.
To check broadband speed, google speedtest.net/ or some other speed test site.
Gluck