[tialaramex]

In https://commonslibrary.parliament.uk/research-briefings/cbp-... under "Why does the price of gas drive electricity prices?" it suggests that, at the time the CMA report linked was written (now over 10 years ago) the CMA thought as much as 40% of electricity is traded at spot prices.

Now, the CMA report that's linking is talking about a world we no longer live in, in that world the UK burns coal, Russia hasn't invaded Ukraine and so on, and thus the numbers might be entirely different now, but that's the best I could find.