There is a long history of using modelling and simulation (M&S) to investigate complex systems. With advances in computing power and simulation frameworks, we can now model and simulate increasingly complex systems, in particular socio-technical systems, which has resulted in M&S becoming an essential technique to aid decision-making. An often-overlooked activity within the design and development of computational models for socio-technical systems, is the development of a comprehensive conceptual model defining the scope of the model with respect to actors, technical resources, environment and abstraction level. With specific reference to modelling large IT and IS implementations, this incurs the added challenges of dealing with qualitative information relating to project scope and implementation processes, along with quantitative and qualitative information regarding the social network of the project resources and emergent behaviours that result from interactions between them. Our approach involves a Multi-Paradigm Hybrid Study to develop a Cross-Disciplinary Hybrid Model of relationship conflict within an enterprise system implementation. We identify that Soft Systems Methodology, Social Network Analysis, Unified Modelling Language are complementary approaches from Operational Research, Social Sciences and Software Engineering, that provide a powerful combination of techniques to develop hybrid conceptual models for subsequent encoding into a simplified Agent-Based Model of complex socio-technical systems.