The sun is shining, the wind is blowing a gale, and just 2.4% of British electricity is coming from fossil fuels. See the live data at https://grid.iamkate.com.
@katemorley have you considered exposing the mix from interconnects? I was pointed to https://www.rte-france.com/en/data-publications/eco2mix/power-generation-energy-source for France, for example.
éCO2mix - Power generation by energy source

Track real-time power generation in France per energy source based on remotely monitored data and forecasts.