Eurovision Voting Map
Countries linked vote for each other more than we'd expect by change.
There's also a link between Spain and Portugal. Other countries do not have reciprocated links.
A schematic representation of reciprocated links between ESC competitor broadcasters (so the UK votes for Ireland and Ireland votes for the UK), based on data from 2011-15. See Weaver's Week 2007-05-27 and 2015-06-07