By Antony Clements-Thrower Elderly people and those with a history of medical conditions are feared to be at risk of strokes and heart attacks as the mercury tumbles heading into the weekend. Brits have shivered in colder temperatures this week as the wet weather gave way to colder conditions, dropping sub-zero overnight. But yesterday the UK Health Security Agency (UKHSA) issued a yellow cold health warning alert as a plunge of Arctic air arrived in the UK and extended it to midday today. As well as the cold weather, the Met Office’s forecast for today shows cool and dry conditions, staying o…