API – Application Programming Interface » Postcoding and Geocoding APIs

Intro

LoqateGBG (formerly PCAPredict)
Address Capture/Address Cleanse. They offer a wide rage of verification and geocoding products including email and bank validation as well as allowing for batch cleansing of existing data.

Sign up now to LoqateGBG’s Services.

Royal Mail

Royal Mail owns and licences The Postcode Address File (PAF) which is a database of all known “Delivery Points” and postcodes in the United Kingdom.

There are over 29 million Royal Mail postal addresses and 1.8 million postcodes.

There are monthly updates and licensing can be expensive with an E-commerce website paying £5000+ for the licence and also a per-lookup user fee for each user of the website.

Google APIs
There is a good article here about implementing a a free postcode lookup service using the Google Geocoding APIs.
As Royal Mail own the rights to the PAF (above) this would be limited to a “type the first line of your address and postcode” type lookup.

http://www.murraypicton.com/archive/free-uk-postcode-lookup-using-the-google-maps-api.php

Doogal.co.uk
Doogal has got a list of all the UK postcodes! The Office for National Statistics released these some years ago so they are openly available. From the Doogal website one can download postcodes as CSV files and could potentially build their own postcode lookup.

https://www.doogal.co.uk/UKPostcodes.php