Broken Hob ?

I have a John Lewis JLBICH601 Ceramic Hob and the hob broke at the weekend. Three of the hobs were on and we heard a cracking sound and they all went off. The hob is linked to the same switch as the oven; the oven still works and the switch also works. I've checked the fuse box and that is also ok. Does anyone have any ideas what it might be?

Thanks