By William James and Andy Bruce LONDON (Reuters) – Britain announced a 25% windfall tax on oil and gas producers’ profits on Thursday, alongside a 15 billion pound ($18.9 billion) package of support for households struggling to meet soaring energy bills. The move, which will give each UK household a 400 pound discount on their energy bill and more for lowest-income households, marks a change of heart for Prime Minister Boris Johnson’s government, which had previously resisted windfall taxes, calling them a deterrent to investment. It is the second emergency policy intervention to help with ris…