The LNG plant is hardly used these days - and it can be replaced with Fraccing!!!
According to the article, National Grid want to increase the size of the LNG terminal, which I think is on the expectation of significant imports from places such as Qatar (how else will QR pay for all the new jets?)
The 3 gas turbine units at Grain are amongst the newest in the UK.
The old oil-fired power station (with the mentioned 244 m chimney) has closed so maybe that isn't the barrier that the article makes out.