Developing robust methodology for the sustainable production of red blood cells in vitro is essential for providing an alternative source of clinical quality blood, particularly for individuals with rare blood group phenotypes. Immortalised erythroid progenitor cell lines are the most promising emergent technology for achieving this goal. We previously created the erythroid cell line BEL-A from bone marrow CD34+ cells that had improved differentiation and enucleation potential compared to other lines reported. In this study we show our immortalisation approach is reproducible for erythroid cells differentiated from bone marrow, and also from far more accessible peripheral and cord blood CD34+ cells, consistently generating lines with similar improved erythroid performance. Extensive characterisation of the lines shows them to accurately recapitulate their primary cell equivalents and provides a molecular signature for immortalisation. In addition, we show only cells at a specific stage of erythropoiesis, predominantly proerythroblasts, are amenable to immortalisation. Our methodology provides a step forward in the drive for a sustainable supply of red cells for clinical use and for the generation of model cellular systems for the study of erythropoiesis in health and disease, with the added benefit of an indefinite expansion window for manipulation of molecular targets.