The notion of software as a service promises agile, flexible and low maintenance system development through a dynamic runtime architecture that allows third-party functionality and capability to be added on demand. There is growing research interest in how service-orientation can be adopted a means for enhancing agility and flexibility in product line engineering. However, integrating service-orientation in product line engineering poses a number of challenges. These include difficulty in identifying services, ensuring services reflect user needs, and determining configurations of services that are relevant in different user contexts. This paper describes an approach for service- oriented product line development that integrates feature-oriented engineering with a self-managing consumer-centred negotiation process to address these challenges.