If they have to submit a meter reading instead of having it sent by Smart Meter
Assuming it's unlikely a meter reader will be physically coming around for a bit
If the cost of what you are using is going up significantly after April 1st and you just have to tell them what you use, I wonder if people will over estimate just to save a few quid?
Unless they go too high and then when a meter reader turns up, they have hardly used any or have even used a negative amount!
I wonder if companies have any algorithms to detect readings that seem to be either too low or too high - in a way to get a lower bill