Not at all fair. If you stop using your supply tomorrow the suppliers fixed costs will still be the same. Like all businesses they should recover their fixed costs through sales charges. i.e. through the usage charge per kwh.It cost money to maintain a supply even if you are not using it. Perhaps the standing charges have got out of proportion but a small charge seems fair.
It would be a different argument if everyone stopped using the service, leaving noone to pick up the tab, but this is not going to happen.
Standing charges favour the rich/high users and penalise the poor/low users.
Example: petrol suppliers don't charge you weekly because they have forecourt costs and refinery costs. They recover these costs in the price of sales.