Looking at it from another point of view it might be that the neightbours have had structural problems in the past. It may be helpful if you asked whether or not they have had to undertake any remedial work in the past such as repointing cracks on the structure closest to the tree. In addition a majority of building insurance companies makes specific requirements that trees should not be allowed to grow with 10 metres of a property. Perhaps you could ask the neighbours if their insurance company have made any stipulations. If the neighbours sold it might also be a condition of the buyers mortgage company that no trees are growing within the 10 metre rule. Privacy might not be the issue here rather trying to avoid any potential unnecesssary repair costs. I would recommend that communication usually proves the best course of action.