My friend lives in a house which shares a wall with another. Those neighbours installed some plumbing which led to leaks and a large amount of damage done to my friend's property. She has it in writing from the neighbour that is is their fault, and this has been confirmed by two surveys. However, the friend's insurance company says that they do not have to pay out because my friend herself is responsible. They are now doubling her premium. Is this right and what can she do?