With FTTN your modem will plug into the existing phone point (whereever that is) the modem then has a phone point of its own that you can plug your existing phone into. Perhaps to make it simpler (and keep only a single phone line into the home) consider this:
1) Where do you want the modem? Either leave it in the Kitchen or have someone relocate or install a single line to the living room (disable the kitchen one)
2) How many handsets do you want? You can have a base point with lots of wireless ones around like this if you want.
3) If you want you could keep the modem in the kitchen. Have someone put in a CAT6 plug and line to the living room. That way you change nothing in the phone setup but you can then plug the modem into the new cat6 plug and plug some other device in in the lounge?