In common with many other systems of higher education, in both developed and developing economies, the UK has expanded from an elite to a universal system, incorporating public and private providers in a mixed economy. The policy drivers for this expansion include government aspirations to improve social mobility and widen participation. Also to compete in global economic markets, and meet greater student demand without increasing public funding for higher education. Inherent within this mixed economy are a number of diversities, of different types, which present challenges to regulators. This chapter will explore the nature of diversities within the UK system and its particular context, with a focus on the challenges posed for quality assessment by the diversity of students and their prior experiences of education, the diversity of providers, and of delivery contexts. The English government has sought to encourage a more diverse system of higher education through its policy to establish a ‘level playing field’ for publicly and privately funded providers, at the same time as creating a market with students at the heart of the system.