For Kettles; half fill and boil the kettle then unplug completely.
Add one sachet to the hot water and leave to dissolve the limescale for 30mins.
Heavily scaled appliances may require a second application.
For Irons; heat up your iron, and, when hot, unplug it.
Dissolve one sachet in enough hot water to half fill your iron.
Pour in and then hold the iron over the sink and steam through.
Refill with fresh water and flush this through until all the residue's gone.
Be sure to test all the residue has gone by ironing an old piece of fabric before using on clothes again.