Good advice to read the broadsheets, but any fool can do that. Formulate the likely topics (Climate Change, Eco initiatives, Defence Spending, role of NATO etc, etc,) into a case which you can present - do you agree with with the popular view or disagree? Construct an argument as to why do you agree or disagree. The interview panel doesn't give a fat rat's arse about your views on wetland conservation threatening the next nuclear power station, but they do need to see that you can hold and defend a view on such things based on rational (or even irrational) logic.