isongutters

We want to make changes to an existing extention which was built right up to the boundary of our property. Our gutter overhangs currently, and if we change, our neighbour does not want gutters to overhang again. So, does any one know best solution for boundary gutters? Pitched roof with gutters on wall. Some say lead replacement and plastic gutters on top. Others say aluminium pre made but too expensive. And condensation and overflow is a problem ??????