Thanks, that's fine i.e. I was thinking of any working from home case. Clearly in some cases one might rely on home network but if it goes down due to a rather unspeakable "quality" of work, then it becomes an interesting case... With such an astonishing attitude (not only the wiring, but the fact that it was simply left there as is and they moved on...), I would love to see how they defend the loss of service in any case...
Let's see, so far neighbour promised to chase them, I shall also signal that they'd better resolve it as it affects both our services in the two flats... otherwise fun will be had, I can guarantee them... as soon as it cuts out due to their esteemed staff's competence...