So much for a quiet day.
Around time the post normally arrives doorbell rang. Was greeted by previous inferior postman (although said postman has yet to cause his wife to scream at me on my own property, so arguably better than Andy). Smugly handed over a letter saying the 'Post Master' wanted it delivered in person. Begrudgingly thanked me and closed the door in face. Evidently he was waiting for me to open it.
Crux of the letter was that "Some residents have noticed one of our staff entering your property resulting in delayed deliveries" and "Her Majesty's Royal Mail would appreciate it if you would kindly refrain from distracting its staff".
Still fearfully annoyed about the letter but have stashed it away so I can consider a response later. Have every belief the suspicious old couple are behind this. Will make sure no neighbourly xmas card is sent assuming I can think of reason to justify to other half.