Neighbour war update:
Neighbour C has received two anonymous letters this week complaining about his behaviour.
Also, the owner of Flat B - which is rented out, and whose tenants are now leaving because of the noise from Flat A above - apparently offered to pay himself to get Flat A's floors carpeted. Flat A occupants refused, and are somehow convinced Flat C guy is behind all of it.
Anonymous letters. Principled stands over carpet. These people are insane.