| Might be a silly question this but is there a standard convention
| concerning the routing of wires in a house?
Yes. But don't rely on it :-)
| I would like info specifically on light switches; so if I am looking
| at a light switch in my lounge, would the wires go straight up,
| straight down or what?
Wires may be run
horizontal or vertical from an accessory
within 150 mm of the top (but not the bottom) of a wall
within 150 mm of the angle formed by two adjoining walls
Cables may be run diagonally but must then be protected eg being in conduit
or having an earthed metal sheath eg mineral insulated cable.