we are currently looking at replacing our gas cooker with a double electric oven, and gas hob. We have a point for an electric cooker, which is protected by a 30A circuit braker.
in your case the 30a supply is more than adequate as you are fitting a gas hob
if you turned both oven and grill i would expect your unit would draw 4 to 5 kilowatts max which works out at 21 amps max