what is the best tool for 50mm hole in porcelain tile

I am fitting a wet room this monday and the down lights are allready fitted, however the whole room is to be tiled in an attic conversion and need to create holes big enough for down lights.The actual small area to be tiled is only 150 mm wide on ceiling so not a problem with tile, but am hoping to have holes on edge of tiles if possible.If not then I would need a 50mm whole in a copuple of tiles.- Any suggestions.