Thought there was a big moth fluttering on the top of the wardrobe but there was nothing there and had to conclude the little noises were coming from the loft. OH investigated today thinking it could have been water but it's dry. No sign of any nest making or droppings or any disturbance to the insulation material. Cavities have insulation in, sofits (I think that's right) are plastic, new and seem completely sound. There's a fan on the bathroom wall that has a ventilator on the outside wall - could a little bird or bat have got in there? If it comes back tonight there'll be a mousetrap up there tomorrow. Any ideas!