We actually have a similar, if not quite so extreme issue with a neighbours Leylandii. There are some trees of similar height (but smaller girth) backing on to our garden (which we bought at the end of last year). It's not been a priority for this year, but I think they need seriously trimmed back or cut down next year. We haven't actually talked to the neighbour about it (their back garden backs on to ours and they are a little reclusive), so it might not be an issue in the end, but it would certainly incur a cost on them to rectify it.
I won't be loosing any sleep over it, but it is definitely something we will be getting sorted next year!