Manganites show promise as magnetocaloric materials - for use in solid-state refrigeration - in terms of cost, durability and tunable thermal conductivity. By tuning the material system La0.67(Ca1-xSrx)0.33MnO3, the entropy change can be significantly enhanced (x<0.15) and this occurs as the crystal structure changes from rhombohedral to orthorhombic. A detailed understanding of how the magnetic, electronic and structural components contribute to the total entropy change is, as yet, lacking. It is this aspect that we wish to address here using a combined theoretical and experimental programme. The key objective is to accurately determine the respective bond lengths in a systematic set of manganite samples which will then be input into our (hybrid DFT) theoretical model to determine the magnitude of competing energy scales in application-relevant materials.