Just a note… I thought my electricity bill doubled this month too but when I looked closely the due dates for December and January overlapped so it wasn’t as high as it looked (still high compared to a year ago). For some reason, probably due to the new year holiday timing my December bill wasn’t due until like the 15th (ish?) but I got my January bill before I paid my December so the December bill was shown as a carry over. It was not late. I assume I’m not the only person with national grid that happened to.