Non-market housing is by definition housing which does not pass through the market. The DCLG paper Delivering Affordable Housing outlines the types of social housing provided in the UK (social and non-market can be taken as interchangeable terms) and identifies the agencies charged with delivery.
Two further reports, the LSE Ends and Means report of 2007 and the Dataspring Discussion Paper 2, give guidance in answering Parts b) and c). The question of what constitutes affordability is a critical one.
For an understanding of the economic principles referred to in Part b) you will the topic of "Consumers" helpful i.e. demand, price elasticity, income elasticity. With this reading it is more important to grasp the underlying ideas rather than pay excessive attention to the detail of indifference curve analysis. You should consider whether the policy of targeting support on housing accords with the welfare aim of giving people free choice in how to spend their money.