It would be nice if it was a unique identifier, but the uk postcode is not, even combined with part of an address like 10, or even 10 high street, sometimes the village is also required to narrow it down. This might have worked for you on a limited set of data, but the assumptions are not valid across the uk.
This seems unlikely. In a small village people know the other house names enough to avoid a collision - in England I've a feeling Parish Councils used to keep order in this regard.
This page suggests that Local Authories legislate (bylaws I guess) on the allowed names: http://www.housenameheritage.com/hnh_extras_officialviewlong....
Quoting that link:
>"The Local Authority will liaise with the Royal Mail to ensure there is no conflict with names of other properties in the same street or immediate area, before formally registering the name. If there is a problem, an alternative name must be submitted. In some cases, the Local Authority may explore the possibility of a house number being registered at this point, in addition to (or instead of) the new name. Once the change has been approved, the Local Authority will normally advise relevant bodies such as the emergency services. The same procedure applies for brand new properties which, for whatever reason, cannot be numbered (however, virtually all new properties today are numbered)." //