UK appliances cap out at 13A, or 3.1kW. Electric cookers may be on higher current wiring, but seem to be rated at 3kW max anyway.
I think the only way most people could get to 8kW continuous without an EV would be to turn on their electric oven, grill, and all spots on their electric hob. And the kettle.
My Danish electricity supplier lets me download my smart meter records since 2022.
It's by hour, and the highest times are probably when I was cooking with both the oven and the hob, and perhaps had the washing machine running too. The highest hour used 2.9kWh.
Plenty of cheap (e.g. rental) homes in the UK have crappy electric shows, which are usually rated at 6-8kW — but rarely used for a whole hour.