A postcode is made up of 4 parts,take BT69 5EX for example:
BT = The main sorting office that handles your mail.*
69 = Relates to the individual sorting office where your postie works from.
5 = This is relates to the specific area/estate of your town.
EX = The street or section of street.
* In practice many main sorting offices have now been superseeded by mail centres that handle mail for very large areas.
So the BT69 area could have many thousand different houses within it,while the 5EX could be one road with one house in it.
I don't think Royal Mail would ever publish a book of postcodes - certainly not for the general public.But I would imagine they do have the answer to your question,you could try asking them!