They aren't per se coupled to gas. Here's roughly how it works:

We work in half hours, 48 of them per day. If you're a very large user (e.g maybe you're a factory which makes cars), or if you choose to do this at home, you can be metered in half hours and billed this way.

In advance of the half hour, we guess how much power we might need. 9pm here soon, I reckon 30GW per the British mainland. Now we run an auction. Everybody who can make power from 9pm to 9:30 bids, saying how much they'd accept to make power

Then, starting from the lowest bids, we add bidders up to 30GW of power, those people will make our 30GW of electricity, and we pay all of them the same price, that price is last bid needed to meet our 30GW goal.

This is often a closed cycle gas turbine because:

1. There are fucking shitloads of them. Probably 35GW nameplate, maybe 40GW, that is a lot of power generation. More than any other single type (Wind can deliver about 20GW to the grid, solar is smaller, nuclear is much smaller, storage also smaller even if you count it as generation which it technically is not)

2. They are (almost, maintenance is necessary) always willing to run, for a price. Rain or shine, night or day, if there is gas at any price they can charge that price plus a little profit to make it into electricity. Only question is if you'll pay

For a typical home tariff the "supplier" you're paying has guessed that on average they'll make a healthy profit if they charge you say 24p per kWh plus standing.

They pay that half-hourly price, if they guessed badly wrong and can't cover the difference they go bankrupt, which sucks for the government who are on the hook to ensure you still get electricity anyway.

So, the de-coupling would happen automatically if the current system stayed the same but you added a lot of cheap storage and enough wind power that on average the country was mostly wind powered. Or indeed nukes or solar if somehow this country built loads of nuke stations or got improbably sunnier.

Right - but if we start getting a useful amount of time when the grid doesn't need any gas, the amount of coupling should start to drop off.