Nope, there's loads of fan assisted ovens that you just plug into a normal socket, I've got one in my kitchen.
Electric oven and hob, or just hob will need it's own supply to the CU because there's too much if all four rings are in use. A fan assisted oven is only one element at a time, either grill or oven
EDIT
I've just googled fan assisted oven
Went to argos, clicked single ovens, the first 6 i checked, Neff, Bush, Hoover etc all were plug in and use