Thanks for the advice
I'm not decided if I will take this sort of business but I will definitely contact my insurance company about my coverage in this area .Also legal advice about the wording .
On the one hand I agree that we should be the authority , but I'm not sure it's worth getting into such a high liability area . Electrical fire seems to be the default answer for investigaters . Even if it was due to an appliance , seems it could open you up to a suit if you have signed off on the house . Worst case , I know , but something to think about .