For a normal House connection(32A)
Lights -1.5mm
plugs(Load-normal,length-Short)-2.5mm
Plugs(load-heavy/Length -long)- 4mm.
Main wire - 6mm if short/10mmif long.
And whats the point going for 3Phase if its a normal house without a heavy load?
if you have 6-7 rooms with AC and hot water etc...