Don't we need NatGas for heating and cooking (considering it's more efficient for those purposes)?
Have to comment on that. Natural Gas is by no means more efficient for either cooking or heating. I mean, let's start with heating. With a good electric heat pump in an environment like the UK, you're going to get an average COP of something like 3. So, in terms of energy in the original source compared to the amount of heat energy entering your home, you could look at that as 300%. For natural gas heating, the best you can get is about 98.5% because some heat goes out with the exhaust. Even just electric resistive heating is higher at effectively 100%.
As for cooking, the most efficient way to cook is actually usually small, well insulated electric appliances. Pressure cookers, convection ovens ("air fryers"), etc. Basically systems where the heat is generated from electricity on the inside of an enclosed vessel rather than having to make it from the outside in. One easy way to tell is if you notice your kitchen heating up significantly during cooking. If you use one of those small electric appliances you'll notice that the air in the room doesn't heat up that much because most of the heat energy is going into the food. With the gas oven or stovetop, it does tend to heat up more because a lot of the energy that you want to go into the food is going into the air instead.
On another point you brought up, on what you do with the excess power, I brought this up in more detail in another post so I'll just cover it briefly here. One thing you can do is use it to make methane/natural gas to reduce your need to get it from fossil sources. As for it being polluting, yes it is, but the primary way it is comes from the greenhouse effect of the CO2. In combined cycle plants, most other exhaust cases like nitrogen oxides are eliminated. Coal, despite scrubbing of the exhaust, releases a lot more in terms of both undesirable gases and particulates.