Hi db,, You are correct the oven is rated at 13amp and the hob is about 25amp, so the hob connects into the cooker unit and the oven plugs into the socket outlet of the cooker unit, it may have seemed a silly thing to ask about the hob, but you would be surprised at what descriptions some people give, your description was correct many aren't, all 4 ring hobs are rated at roughly the same so it is no problem to just change it to a ceramic type, good luck, and welcome to A/B, Ray,
PS
Make sure you use heat resisting flex for oven.