I really have looked into the PIR route and it's not a goer based on the position of the switch and the layout of the bathroom. It would involve lifting up the boards in the loft (and removing all the junk etc). Also, who wants to leap out of their hot bath and jump up and down dripping wet to get the lights to turn back on? I have also found that the GU10 replacements I bought, don't fit in our luminaires. I've now removed half of the lamps but it still drives me nuts when I have a pv array on the roof trying it's damnedest to give me 200W on a dull day, to find half of it is being used to provide lighting in an empty bathroom! I just want a timer!