Going to the media could be another option. Chrous would probably shut up pretty quickly if it got decent media coverage.
Makes me glad I was present the entire time for the fibre install at my inlaws (who I am currently living with). The contractors were probably annoyed at me hovering but if my hovering encouraged them do the job properly I'm happy I did so. I presume the OP's neighbour had their install done without anyone monitoring/checking the work done.