My bathroom is lit by several 12v 50w downlighters which makes it rather bright when trying to take a relaxing evening bath. Can I replace the standard switch with a dimmer? My main reason for asking is that the extractor fan is wired to come on when the lights are switched on and I'm not sure if the dimmer will also reduce the power to the fan. There is a separate fan switch next to the light switch. Sorry if I'm being dim - pun intended!!