Perhaps you can clarify the issue , if you are ‘changing over’ to a 900Mb full fibre service, suggests you have or had a different type of service ( possibly ADSL or FTTC , or with a non Openreach based ISP ) who was this previous service with , was it BT ?.
Not every customer upgrading to full fibre with BT will need a new hub ( router ) presumably you do need a SH2 because ( if BT were your provider ) you didn’t already have one with your previous broadband , they are sent out by ‘mail’ , the time of year ( Christmas) and the current individual action could have a baring on the delivery time.
Was the rest of FTTP successfully installed, ONT with a steady PON light lit etc. , if it is then hopefully when the SH2 arrives, as soon as it’s connected you should be good to go, if your previous service has already stopped working , presumably it was necessary so that your FTTP will work as soon as the router arrives and is plugged into the ONT , the alternative presumably would have to not complete the FTTP install ( well the authentication part ) , that may have maintained the previous service, but that would mean you would need to book a new installation date etc, but it’s not clear ( to me at least ) if you have no service at all , or are just disappointed that the FTTP is delayed, but the previous service is still working.
