Upgrading to fibre this week, should I be worried about need for extension

[#1]

I moved from sky to pn only this months and immediately found pn offered me fibre whereas sky don't, so upgraded immediately.  Install due Friday coming.   Thing is I have an old house with the old GPO phone box now mounted in what is a downstairs loo.   I run a phone extension from it to my meters cupboard on the other side of my hallway hidden behind some plastic routing given no power in the loo of course.  I then have the current pn router and an 8 port gigabit hub feeding many links in the house.  
I ordered the extension install for fibre but worried it may be ugly or not achievable given my setup.  Also I won't be at my property, my wife will, and thus my fussy nature of clean installs won't be present 
What's the story on the extensions? Can pn use the existing one? Can they bury a new one in the current masking route?
Finally I ordered a new router with the install as wasn't sure if the same one as adsl on pn, are they the same?
Thanks for any thoughts.  

[#2]

The routers are different so you were correct to order a new one.
I'm sure that the engineer will put the new cable in the ducting & position the modem by the powerpoint & connect it to the new BT socket. Ask your wife to smile sweetly & have the kettle on & I'm sure everything will go OK. She might even listen as you carefully explain to her exactly what needs to be done!!

[#3]

Cheers very reassuring.