I had the fibre upgrade yesterday. Only thing they had to do was replace my existing ONT as the one I already had was only 1GBit so that had to be swapped out for a 2.5Gbit one. The most time taken was the engineer getting it to connect and had to resort to ringing up to pair the ONT number to my incoming fibre connection. Once done that was up and running that was it. Plug the new router in and check it was working. Job done. Bet the Openreach engineers wish all their callouts were that simple.