Citroen Xsara Picasso interior light turning on during day whilst not in the car, battery light on, wipers going whilst not in car

My car electrics seem to have a problem. The interior light sporadically comes on and off, draining the battery. Also, someone saw my windscreen wipers going whilst I wasn't in the car (I'd left them in the on position but they shouldn't go whilst the engine is off. I've taken the bulbs out of the interior light but the car still starts in economy mode most of the time and when I open the car, the battery light is on. I have fitted a new battery but it makes no difference. I have taken it to the main citroen dealership in Manchester, who have done all the diagnostic tests and say everything is fine. Any ideas?