At current prices, to power the UK for 36 hours off battery storage, it would cost (according to Gemini) £150bn to £400bn for the batteries alone - that doesn't include purchasing land, wiring them up and so on, nor the cost of the wind farms and solar panels to feed the batteries. We don't/can't/won't do hydro pumped storage in the UK.

Sizewell C, our massively overpriced nuclear power station, comes in at about £100bn.

It comes in at £100bn for 3GW - that's about 7% of total UK consumption. A huge amount to be sure, but the choice isn't £100bn for Sizewell or £400bn for batteries.

Rolls Royce SMR for Czechia at 0.5GW is about £3bn

To be clear - this doesn't exist. They "aim" to start construction in 3 years and it's a FOAK project so will surely be delayed. The initial target was a cost of £2bn - the paper cost has already increased by £1b without a shovel turning over a single grain of sand.

It's a huge shame and problem across the 'West' - but we can't build megaprojects for anything resembling a reasonable cost any more.