Ovens in the UK are usually wired in. Plugs go up to 13A, suitable only for small (e.g. tabletop) ovens.
You usually do not plug an oven into a standard 230V socket in Germany. They are connected to 3 phase outlets with 400V and up to 16A, which is nothing to sneeze at.
3 phase for ovens? That seems totally overkill to me.
In France even though they're not usually plugged into a standard socket, all the ovens I've used ran on standard single phase current. Houses are almost never wired for 3 phase anyway.
Parent was talking about toaster ovens though, and those are (as far as I know) always plugged to normal sockets.
They do have a higher current rating than the French and German standards (30A vs. 16A) but even those do support up to 4 kW. Ovens also run at 3 kW or so in France and Germany.