UK Address Data
<postcodes.io>
Several APIs for returning mainly geo information based on postcode inluding:
- Random postcode
- Validate postcode - returns simple true or false
- District / LA data
http://www.royalmail.com/find-a-postcode
Royal Mail postcode finder which narrows results as you type, providing an immediate total of any matches including whole of address and partial words. The api returns 7 matching results whilst a partial postcode is provided.