Exploding stars, or supernovae, are important probes of the extragalactic universe, from finding the lowest metallicity environments, to studying the large-scale dynamical effects of dark energy. However, many aspects of supernovae as a population of events remain unclear, including the variety of supernova types, their luminosities, and their progenitor stars. This project will use data from two large, recently-completed surveys of supernovae - the Dark Energy Survey and the OzDES survey - to probe and understand the statistics of the supernova population. These data, on thousands of supernova explosions, will be the first census of the high-redshift explosive transient population, with a particular focus on the diversity of the core collapse supernova population. These results will then be used to prepare for two major new facilities that will revolutionise the study of supernovae. The first is the Large Synoptic Survey Telescope (LSST), an 8-m survey telescope that will image the whole sky every 2-5 days, and which will find new supernova explosions at an unprecedented rate. The second is the ESO 4MOST multi-object spectrograph, which will study thousands of supernova explosions and their host galaxies in great detail as part of its TIme Domain Extragalactic Survey (TIDES). Our project will provide the data needed to optimise these two experiments, enabling us to ensure that the combination of facilities will provide the ultimate cosmological sample of type Ia supernovae, and probe completely new parts of time-domain parameter space.