On UK post addresses (mostly junk mail) are 5 digits to do with the address. What are they for?

Question

This is not the Post Code. They are usually above, or to the side, of the actual address.

Answer 1

They make up the Mailsort, which is used for automated sorting. Three Mailsort products are available - known as 120, 700 and 1400 - each based on the customer's ability to sort into increasingly smaller geographical areas.