Its good to know how to about electrical safety, especially around the home. I am a qualified electric but even I can get it wrong if the home was built with a pre-1970 ring main system. Last time i worked on such house a fitted a new light fitting in the living room which also tune on the bathroom light upstairs but turned off the toilet light in the next room !! Took me days to figure out what was wrong. So, the moral of this story, Call in someone else to do the work so they can sort any problems to save you the trouble.