We introduce Grid Resources for Industrial Applications (GRIA), a project that aims to enable commercial use of the Grid. GRIA enables service providers to rent out spare CPU cycles, and clients to hire those CPU cycles. Web services play a key role in the architecture of GRIA, chiefly through their interoperability and security features - they provide a well-defined means of limiting clients' access to discrete operations, thus allowing clients to do "work" on a remote application server without giving them full shell access to the server. In this paper, we focus on requirements, business processes and security, and interoperability and standardisation issues raised by this work. We also describe some of the lessons learned through experience of designing, implementing and