Having an extension built... En suite bathroom (bath, shower, 2 handbasins, toilet) 3.2 X 2.3 m. How many 12V halogen downlighters should I have? And what wattage? (Plan to have them on a dimmer). Is there a general rule for how many LV halogens are needed? There will be new ceilings in our hall, kitchen, utility room and bedroom and we plan halogens in all these but don't know how many. Does anyone know a good web site for such advice?