Can anyone tell me if diesel/petrol generated electric is cheaper than my power supplier, SWALEC, in the UK?

I am looking to save money on the electric/gas bill this winter and am considering a diesel generator to supply domestic power at 240 volts.
Is this practical?

Home made electricity from a generator is more expensive than that from a supplier. They get huge bulk discount on fuel and their equipment is way more efficientt.

But, and this is quite a big but.. if you also use a heat exchanger on the exhaust and use the engine cooling system to heat your house, you win hands down. Think of it as either sightly more expensive electricity and free heating, or slightly more tricky heating and free electricity.