if it's from the main board to the fuse box then it's your responsiblity if it's from the main supply to the main board (where the meter is) then it's you local electricity distributor and they would have to do this as an emergancy job which means up to 2 weeks (electricity not being considered as high a priority compared to gas).
it wouldn't necessarily be an emergency job if a) the customers are still on supply and b) there is no immediate safety risk. i think such work is more likely to come under planned work, which, if there are relatively few customers involved, could take a long time to get sorted
