we do say toilet, there are signs up on toilet doors saying toilet. loo is another word for toilet. and toilet is another word for Water Closet (W.C.) which came from the time when the Toilet on trains was integrated with the 'water closet' (or room with sink). WC was kept as a uniform name. We say bathroom for a room with a bath and (usually) a toilet and sink in it. and toilet room for a room with just a toilet and sink. Interestingly a room with a shower is usually called a bathroom too.