Thanks ClubmanThe fibre ONT (Optical Network Terminal) and provider's broadband router both use wall plug power supplies so if the mains is out but you have an alternative power source then you just plug them into that same as any other device. But if a local power outage also cuts power to the local cabinet or other parts of the network infrastructure then you're probably offline anyway
I know some time ago we had a local Power cut My house which no longer had a Copper phone line lost SKY Broadband,
next door also had a power cut at the same time still had Broadband,
Spoke to SKY today now looking for 45 for 1 GB and 39 for 500MB,
Thanks everyone for your help, I am no longer up to Date on some of the techinical end of things,