[Margaret Pilkington]

Cashy, if your energy supplier needed to install new meters for safety reasons(because your current meter was outdated) then you can ask for a dumb meter...this is the same as a smart meter, but it is not connected by a SIM card to the suppliers network.

These supplier networks are supposed to only accept messages from the supplier and are encrypted. This does mean that your energy supplier could(in theory and at times of high demand) instruct your meter to cease supplies to your property.
Now with conventional non smart meters, I don't think that is possible.

You might think this scenario would not happen, but as there is a move away from power generated by fossil fuels in favour of energy produced in other ways( wind turbine for instance) I can see a time coming when there will not be enough energy to go around and selective areas may be targeted in reduction of power supplies.

A smart meter is something that is installed in your home, on THEIR network, for their benefit.
Who is to say, in the future, how the information collected will be used. It may even be sold on to third parties who sell things like domestic appliances.