ah yes, the limescale. We cleaned ours last weekend with oust applicance limescale remover, sachet format, worked a treat.
If your water is hard, it'll start affecting other appliances too like irons, washing machines, dishwashers. For longer term fixes, you can get water softeners, or use a water filter jug for filling the kettle and iron, we have one of these and find we only get limescale buildup around the time the filter needs changing.
Longer term fixes include fitting water filters on your water source feed to the house. theres already a few posts on AAM if you want to search.