The Migration Observatory have published, A Decade of Immigration in the British Press, covering 2006-2015. The report finds that national newspapers moved their focus from illegal immigration to the scale of legal immigration and the need for “control”. It also highlights that nearly half of all stories analysed relied on statements or arguments made by the journalist themselves, rather than reporting the views of external sources (e.g. policy-makers, think-tanks, etc.).
The report is available at: http://www.migrationobservatory.ox.ac.uk/resources/reports/decade-immigration-british-press/