This paper summarises research into localised urban systems which accounts for variations in styles of diversity within multi-cultural cities. New work builds on previous studies in London and Turin. The first produced an ideal type model of open:closed urban systems and evidence that the former have better capacity to incorporate incomers. The second revealed the need to adapt the model to account also for the process of diversity. This third phase combines ethnography with computer simulations to reveal emergent properties as well as present styles of urban systems, and to rank the variables driving change. The outcome will be a typology for users dealing with migrant settlement and urban regeneration.