They usually run up sleeve on the screen, if your roof lights have a seperate switch to give them power and your ensuite stuff works when that switch is off then a good chance it has its own run and you should find it in the run up the screen, if not then they are piggy backing off the roof light circuit which would mean the ensuite would be powered possibly from the nearest light to it, checking the back of the light would show if its got a run off it, with a meter on the ensuite end disconnect the feed from the ceiling light and see if it goes dead then at least you know it won't short...... the roof feed can have TV lead, power for TV antennae, ceiling lights I just can't remember if another for ensuite but I think the couple Ive looked at needed roof light circuit switched on............
They can be that skimpy on wire that on a hot expansion of things will disconnect a switch.