I work with prints here at a NUKE generating plant in the states. Here is what we have. Make above view layouts of the rooms/floors in the bldg. Determine a symbol for each electrical component (ie "$" for a switch, @ for an AC receptacle (we use a circle with 2 lines through it )). Duplex receptacles would have 2 symbols together, one on top of the other. Now, walk through each room and locate all the electric devices. Don't forget the lights. Place the appropriate symbol at the correct location, on the drawing of the room layout. Do this for all rooms, closets, cooking range, fridge and other appliance recepts. (high volt recepts should have a seperate symbol). Flip switches to identify switch/light combinations. Then, draw a slight arc connecting the switch symbol to the light symbol on your drawing. (the arc distinguishes the circuit, since the room walls would most likely be straight lines). If you have switched recepts you would do the same with a small lamp, plugging into the switched recepts one at a time. The next trick is to identify the circuit or breaker feeding the loads. This is best done with more than one individual. Turn all the lights on in the area. Open the labeled breaker, or the one you think it is. When the lights go out in the room, have your friend yell to the individual at the feed box to stop cycling breakers. Identify the light/lights that went out by placing the breaker number (B1, B2....) next to the switch/light symbols. Repeat this for all receptacles using some plug in lamps. For hot receptacles, draw an arc to tie all the recepts together. When done you can relabel all the breakers with accurate descriptions, and your schematic can be redrawn while you enjoy a stout ale. Good luck to you & British Energy.
Mark