Existing further and higher education (FHE) buildings urgently need effective retrofit strategies to meet net-zero targets, despite limited historical data. This research integrates LCA, techno-economic assessments, and modelling to identify optimal interventions balancing envelope improvements and low-carbon heating. It considers factors like cost, user comfort, climate change, and evolving energy grids to achieve significant carbon reductions. Considering the inherited occupant thermal comfort benefits of the proposed building retrofit options, the study outlines results that reduce not only operational carbon but also embodied carbon from retrofit work to the end-of-life of the building (60 Years). A fast carbon reduction approach, such as converting to heat pumps, can cut operational energy by 100-118% and GWP by 97%, but increase operational energy costs by 80-101%. Although choosing between specifying synthetic over natural materials can impact project costs, the differences in whole-life carbon emissions provide a 27% and 31% reduction in carbon without considering a change in heating system (and fuel type). Over time, during replacements and maintenance periods, these can play a more relevant role. Switching to lower carbon heat pump refrigerants has shown marginal carbon reductions; however, it is hoped that this technology can find other improvements in lowering its embodied carbon footprint. This research has shown that implementing combined retrofits by integrating heat pumps and envelope improvements, offer optimal cost-effective, emission-cutting solutions for university buildings, enhancing comfort and prioritising natural materials and optimised heating technology. The study provides a detailed comparison of retrofit solutions to inform holistic decarbonisation strategies replicable across different building archetypes.