Yes, there are chemical cleaners out there that will take off limescale but they will also kill off the bacteria we need to make our fosse septique sewage system work, and then flow out and pollute our land - so they are not an option here. The horrid fact is that it just takes elbow grease every week - Ben's elbow grease to be more precise.
You're probably sitting there thinking that's unfair and why aren't I taking a part in this scrubbing exercise. Well, the truth is that I want a dry-toilet in the house, a composting loo. I've said that if we have one I will make myself responsible for emptying it because it's a whole lot easier - and pleasanter - than sitting with your head down the loo scrubbing off chalk! But Ben insists (for the time being) on keeping a conventional toilet so it's his job to scrub. Lucky him!!