@Tim: Well said, Tim.
Tim, contrary to the garbage from some others, you are SPOT ON.
Electricity generation capacity must match electricity demand, at any moment in time, give or tack a Dinorwig or two (www.fhc.co.uk).
So there already is, and must be, a hierarchy of generating capacity which can be switched on and off as required so supply matches demand (there's very little research gone into making demand follow supply, afaik, other than so-called "interruptible contracts", but that's another story).
Nukes take days to warm up and shut down in a controlled way, so basically you have to leave them running 24x365 (give or take faults, maintenance, etc). Coal and big oil and gas are a bit quicker, taking hours (rather than days) to reach full power.
Meanwhile, the hundreds of gas-powered CCGT power stations around the UK  as introduced by the lunatic "dash for gas" which followed Thatcher's electricity privatisation, are **ALREADY** used for short term peak following and are **ALREADY** going through thermal cycling once or twice a day, because they are able to respond within minutes, but you have to turn them off quickly once you don't need them for peak use, because the (soon to be imported) gas they use is too expensive to use for anything except short term peak lopping.
Very poor research, very poor article. Sorry Lewis, not up to your usual standard.
 Not in Northern Ireland 'cos gas is expensive there