There is a round valve to the aircon in the back of the glovebox but you will struggle to get it tout.
Behind it is a flexible pipe that leads to the side of the heater and carries the chilled air.
You could use this route for the cable but it would mean that the chilled effect would be gone.
Better would be to use the rectangular bank also in the back of the glovebox.
It is item no. 05 BLIND PLATE, HAND LAMP here :- RealOEM.COM * BMW R50 One 1.6i GLOVE BOX
You could run the cable through the hole it leaves and keep the chiller function.
Hope this helps, WELCOME TO MINI2!