sounds like the switch is faulty quite easy to change only couple of quid from wilkos providing it is only 1 switch in bathroom it is a 1 way 1 gang pull switch to change it turn fuse off in dis board (fuse box) if not sure which fuse always best to turn of electric with main switch upon opening light switch normally 2 screws you should have 3 wires yellow/green that may not b connected up this is earth because it plastic u dont need it but dont cut it out now the other two wires could b both red or one red one black the red is a permanante live n blacck is a switch live if u change switch it really does not matter which hole to stick red /or black in but really if switch marked common its the red that goes in that one n put the other colour in other hole jobs a gud one remember to turn electric of cause u will get a shock and its not pleasant had a few myself remember to make sure the terminal screws are tight to reduce sparking you cant get it wrong its that easy but if you are not sure its always a gud idea to seek a compatant electrician gud look
wayne the friendly sparkie, May 2007