If you mean will you have to change the username and password for the Broadband login for each of your pals - yes, of course you will as you will need to connect to their broadband service.
You will also need to have a micro filter on the main junc. box to connect the router to and make sure that any other router is disconnected first.
As for the bell wire (wire 3) I don't know how familiar you are with this, but it is quite feasible to disconnect this entirely (as long as all of the equipment connected is modern and up to spec). Just google for "disconnecting bell wire on bt socket"