What is the procedure to run an electrical supply from main residence to a brick built outhouse approx 30yards away, to supply lighting and power outlets. what is the best cable and routing and is extra earthing required.
Use armoured cable. The size is dependent on what you plan to run in the outhouse, but I would use 10mm. One end connects to a 40A MCB inside the house. At the outhouse end it should go to another smaller consumer unit with 6A & 32A MCBs for lighting and sockets respectively. The outhouse consumer unit should also include a 30mA RCD.
Because the cable is armoured it can be routed almost anywhere and can be buried if you wish.
howtomendit.com for free repair help, information and advice.
Try fixfault.com to fix lighting.