Hi folks,
just posting about an excellent tool I came across, from Rob Whittaker (https://osm.mathmos.net/):
OSM Post Office Progress in the 'BT' Postal Area
Rob has gotten hold of the official Post Office Ltd dataset, and runs a comparison with what’s currently in OSM - in other words, he has an excellent map and table of missing Post Offices.
As I type, just over half the Post Offices in Northern Ireland aren’t mapped in OSM.
I’m sure we can improve that situation 
I started off tackling County Down, which is now looking a lot better!