You can see spot prices at the top of grid.iamkate.com for example.

It would be nice to have some belated insight into how the bids look. Like maybe a few random hours released from a week ago?

Oh, and it's half hours. You can't buy or sell five minutes of electricity, just half hours, which is why your smart meter also thinks in half hours. 48 periods per day.

Aha - that led me to https://bmrs.elexon.co.uk/system-prices , which shows that for the last week prices have been hovering in 80-180 range, and there was only one period of negative pricing during the day.

Wow, £100 per MWh and 12% is fossil fuels in the mix at 10:48am ... a bit more Solar adoption and maybe that 12% could go away, it's morning after all.