I need my toilet fixing and replacing

I need help with my toilet cistern, which appears to be leaking. The job involves either repairing the existing cistern or replacing it entirely, depending on what you find to be the best solution. I'd like a professional to assess the issue and advise on the most cost-effective way forward. The toilet is in my main bathroom and is easily accessible. You'll have full access to the space and can bring whatever tools and materials you need for the work. I'm looking for the job to be completed efficiently, with the toilet working properly afterwards and no leaks. Once finished, I'd appreciate a brief explanation of what was done and any maintenance tips to prevent future issues.