I have a power socket fitted outside ( by builder) I want to build a shed on the side of the house, the question I want to ask is if I wanted power in the shed and also a cable running into the garden to power some lights, if I used arnoured cabling and tapped of the back of the outside socket to the the shed were I fed this cable into a consumer unit with 2 RCD breakers and then ran a cable into the back for the lights and the other cable for a socket in the shed, would I be doing it corrrectly or is there a better way to do it. I still want to be able to use the original socket to plug in lawn mower etc..