i've just done a connectivity test on my lawnmower cable, one cable is reading 12.5 and the other is 11.5, i know its meant to be as close to zero as possible, so does this mean the cable is knackered?
11.5 and 12.5 What? Where were you measuring from, to?
This is nothing personal since I do not know you, I suggest you watch more YT videos of how to use a multi meter, and check other simple things with the idea to gain experience, then you will eventually gain a better understanding of what you are trying to do. (And see the "errors" in your question and the information you gave.)
The test should be a Insulation resistance (IR) on the cable & the reading should be a minimum of 25 M Ω for equipment up to 250v. If you don’t know how to use or read electrical test equipment, get a competent person who does.
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!