Replacing cheap electricity from coal with costly and unreliable electricity from windmills will mean more people freezing to death in the winters because they can’t afford electrical heat.
It won’t happen unless they greatly build up their natural gas power generation.
If you read the details of the speech, that’s not what is said: the emphasis is on nuclear and gas from fracking, not wind. If anything, wind is being played down, with the UK government already having announced that any further wind development will be almost entirely offshore, not on land.