The UK relies far too much on gas turbines, rather than renewables and as a consequence we have energy costs far higher than other European neighbours.
Gas is not cheap, it basically doubles your costs.
Renewables require gas in the UK. There is no realistic route to 100% renewable grid without gas currently. I did some modelling of this and you'd require something on the order of 4000GWh of battery storage. We currently have 40GWh.
Gas is far, far cheaper than building ~£1T worth of battery storage. Even if prices dropped, you are still looking at multi-hundred billions, and you still need the renewable capacity on top of that.
Arguably if we had spent the £100bns (in subsidy and transmission upgrade and curtailment costs) we've already spent on renewables on nuclear instead we would have a very clean grid, even at crazy UK nuclear build prices, and stable electricity prices.
Well the goal is to only run the backup a few hundred hours a year, the question is which technology can provide close to 100% of demand a few percent of the time in the cheapest way. Turbines or even gas motors are relatively cheap in capex and gas is easy to store in large quantities.