If the hot water to the taps is still ok - for example not too hot or hotter than normal - then it is probably just with age and the constant heat. You can buy cylinder jackets for insulation.
If you think the water is too hot or to check - try turning down the cylinder stat and use a thermometer to check the stat is working and the water temperature does drop. This will rule out excessive heat (over heating) being the problem.
DIY how to tutorial projects and guides - Did you know we have a DIY Projects section? Well, if no, then we certainly do! Within this area of our site have literally hundreds of how-to guides and tutorials that cover a huge range of home improvement tasks. Each page also comes with pictures and a video to make completing those jobs even easier!