With thanks for your 'heads up', broadgage, I will tomorrow morning fill up my 5 litre green can with motor mower petrol (it's stored in the garage), the car (it's parked out on the drive) and I will also stock up with barbeque charcoal (also stored in the garage). We have gas central heating, so I'm unable to panic buy that. 

Do you have any other heating, apart from gas central heating? or electric heaters.
If not it might be worth buying a portable heater that uses paraffin or bottled gas. And fuel for at least a weeks heavy use.
Any serious crisis is liable to interrupt electricity supplies, as a lot of our electricity is still from gas.