Volkswagen Polo washer and wipers going continuously

Hi, A few days ago my windscreen washer came on by itself and then also the wipers, infrequently at first tho often coinciding with hitting a bump in the road and once when I used my indicator!? Anyway yesterday both washer and wiper stayed on permanently and so I've had to disconnect both from the battery. I imagine electrical faults can be hard to trace.. but before going to the garage man thought I'd ask if anyone has had similar problem or can suggest a remedy.
Many Thanks
Morgan