There was a change recently to a wikipage dealing with this topic (URL follows)  - does the step-by-step instructions happen to match your method?  Or can you suggest an improvement on them?- https://wiki.openstreetmap.org/w/index.php?title=Proposed_import_of_UK_postcodes_and_UPRNs_(England_%26_Wales)&diff=next&oldid=2881160 