2017 update since my previous post:
UK General Election – Voting Distribution Map 2005/2010/2015
Now available via Wikimedia: 2017UKElectionMap_votes.svg
Source
git clone https://github.com/eelcodevlieger/mapimage.git
Main class: com.knocksfornometer.mapimage.Main
Input Files: src\main\resources
Output Files: target\map