If your teasmade is affected by limescale, this can be treated with a de-scaler from your local ironmonger or DIY shop. Furring of the kettle spout was a recurring complaint received by Goblin in the 1970s. In June 1971 Goblin’s Mr D M Barber summed up the company’s view on such complaints.
With regard to the furring of the spout, this is a problem which has always been with us to a certain extent and the furring of the spout is of course accentuated by the fact that the concentrate of the residue from the bottom of the kettle is passed up the spout and tends to cling to the sides of the bend outside the kettle which is already up to water temperature. The only answer to this problem is regular defurring of the kettle, using the formic acid defurring agent known as Kay-Dee which is usually obtainable from ironmongers in a hard water district.
We do customer service a little differently these days. Here’s a video from Swan on how to descale your teasmade with their own proprietary descaling fluid: