P6 heater wiring

The p6 project continues, when I can stand the cold. I’m trying to sort out the heater wiring, having removed the aircon and fitted a heater box. These seem to be the control wires under the dash. A double earth, and small brown with black stripe and a larger brown with yellow stripe. By earthing the brown/black wire the fan spins at slow speed. Should the fan spin at fast speed when I earth the brown/yellow wire?

Also, what are the white/blue and white/yellow wires for?