As others have pointed out the electricity price is only set by gas when gas is needed, but that's only part of your bill. Renewables now make up over half of UK electricity generation and they are financed through Contracts for Difference which are ultimately paid for by a supplier obligation levy on electricity bills.

When market electricity prices are lower than the strike price for a CfD, electricity users end up paying the difference through the levy and when the market price is higher it reduces the amount levied. So for the renewable portion of UK electricity generation we effectively pay the fixed strike price of the CfD whatever the market price.