2017 update since my previous post:

UK General Election – Voting Distribution Map 2005/2010/2015

Now available via Wikimedia: 2017UKElectionMap_votes.svg

Source

Map Image source code in GIT

git clone https://github.com/eelcodevlieger/mapimage.git

Main class: com.knocksfornometer.mapimage.Main

Input Files: src\main\resources

Output Files: target\map