There is an excellent resource to see the real-time energy sources of the UK National Grid. There is a complete breakdown across all of the energy types – fossil (gas), renewables (solar/wind/hydro), other (nuclear/biomass) as well as interconnects to other countries.

The site is National Grid: Live (https://grid.iamkate.com/)

There is also a section for historic data, which has statistics for the last 24 hours, week, month and year.