Create A UK Post code Script

This is an easy project for a good coder who knows what they are doing. I want to be able to create a script that will allow someone to input their post code(e.g.: Mk44 1rl) (UK ONLY) and then based on the input it will search a list of post codes of events and then list the 2 closest events by distance. I am not sure where the coder will find the postcode list and how to calculate the distance etc to produce the desired result. The winner coder will need to research the various scripts and databases to make this work. Once complete the script will sit on a webpage that will be a lead page that is hosted in a service like click funnels so will need to be a php script that pulls data and then does calculation to provide the personalised 'here's your nearest workshop' page.