Media exposure has become increasingly complex and hard to measure with the rise in online news consumption. Furthermore, since many people now routinely access news via social media, questions arise as to whether social news-sharing is affected by the polarization and partisan echo chambers that are often observed in social media communication. This study considers news-sharing on Twitter during the UK General Election in 2015, using the act of sharing as an indicator that the sharer has been exposed to that online news content. Analysis of the network structure of users and the news articles they share identifies multiple distinct user communities, which are characterized by analysis of the articles shared within them. Communities are characterised by news article sources (web domains), geographical origin and content; time of article publication was also considered but showed no significant relationships. There is evidence for ideologically biased audiences that predominantly share content from either left-leaning or right-leaning news sources, but these audiences also see content from opposing viewpoints. Other audiences are characterized by geography and/or specialised on particular news topics. Overall these findings suggest that many people consume a diverse range of news content over the election period and that the level of political bias in content exposure varies widely across the Twitter user population.