Delayed start is common for washers but not for clothes dryers (as you really don't want wet laundry just sitting there in the appliance for hours..)
They turn over and blow cold air periodically to prevent them getting stinky.
As opposed to having your clothes be in a wet clump for hours? Between the two choices I'd prefer it being dry, because I know at least there will be less microbial activity.
30p/kWh in the day, 12p/kWh at night.
Dry an entire load for less than the cost of a Day Rate kWh, simply by pressing the "delay" button a few times.
It’s not common to have separate units here though. Much easier to setup a wash/dry cycle timer.