I said it wrong. It's not a ceiling rose in the bathroom but just a pull cord switch but I was wondering if there is anything in one of those ceiling roses that can trip. I haven't been touching them. I reckon to access roses I need to go to the loft.It's unusual not to have a black neutral wire at a ceiling rose, or rather, unusual to have the neutral as red. Are you sure there aren't any other wires that might have escaped from that ceiling rose?