Ok.
First things first.
How big is the data thing?
Because there are a lot of postcodes in the UK and that file is huge, from memory.
I think an easy thing to do would be
List 1 : all the postcodes in the area you are looking at
List 2: all the postcodes in your map
List 3: all the names and their postcodes
First:
Are all the codes in L1 in L2?
Are all the codes in L2 in L1?
Ok.
First things first.
How big is the data thing?
Because there are a lot of postcodes in the UK and that file is huge, from memory.
I think an easy thing to do would be
List 1 : all the postcodes in the area you are looking at
List 2: all the postcodes in your map
List 3: all the names and their postcodes
First:
Are all the codes in L1 in L2?
Are all the codes in L2 in L1?
http://chandoo.org/wp/2010/06/17/compare-2-lists-in-excel/
https://chandoo.org/wp/compare-lists-excel-tip/
But yeah, give us a quick table or something and I'm sure someone will sort you out.