Tidying up addresses database - removing redundant variant records

Good morning/ afternoon

I know that the following could be more tidy. Forgive my transgression in this regards and any assistance you can provide is greatly appreciated.

In short I have about 25,000 entries of addresses to trawl through (again - already did this manually 6 months ago), tidying any redundant variants out - and am looking to save myself a lot of manual trawling

Sample of Excel Data Attached - pre and post-processing:Sample.xls

/\/\/\/\/\


What I am personally hoping for is advice and perhaps snippets of code that could:

a) Firstly determine the 'alphas'

(start pseudo code)

If current record in list is identified as an official record (H),
Identify the closest match to current official record's Street (D) (and Prefix (C)?)
where the Locality (E) is the same,
and assign the same official database value (G) to the same column of the chosen record (G).

(end pseudo code)

b) and... once the 'alphas' are determined: (and optionally with the removal of 'officials' from the picture'):

(start pseudo code)

If current record in list is identified as an 'alpha' record (G)
Identify all records of adequately similar match to current record's Street (D) (and Prefix (C)?)
Where the Locality (E) is the same,
and assign the same official value of the alpha (B) to column (F) of the variant (to facilitate database update)

(end pseudo code)

SOS?