Good advice Colin. I have had one on my inlet pipe for years. I does not stop the lime but it reduces it and makes it considerably easier to remove as it's soft.
It's a unit from Scalewatcher in Henley on Thames. It consists of a coil of wire that you wrap round the cold inlet pipe and connect to a mains supplied box. It costs pennies a year to run, in fact you forget it's there. It takes about ten minutes to fit and you don't have to cut any pipework.
I rarely clean the kettle out and even then you only need a washing up brush. The kettle has survived more than ten years of Spanish water.
There are similar ones available but I can't vouch for their effectiveness. Scalewatcher is the original.