Unable to answer "What’s the house number of this building?" – Williams Park Caretaker's Cottage (Detached House) – https://osm.org/way/844891866 via StreetComplete 57.3:

Building has been demolished
https://www.huttcity.govt.nz/environment-and-sustainability/parks-and-sportsgrounds/parks,-gardens-and-reserves/williams-parkdays-bay-beach