So all you have done is relocate on ceiling light, that required one cable only extending??? Nothing else???
You have obviously done something wrong! Have checked that all conductors are terminated tightly and also you have not trapped insulation in the terminals?
If section of your lighting do not work, after alteration to a light on the circuit, this usually boils down to either the live loop conductor or neutral loop conductor being loose/disconnected or possibly both of them.
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!