LONDON (Reuters) – British finance minister Jeremy Hunt is considering a big increase in a windfall tax on oil and gas firms and extending it to power generation firms as he tries to find ways to repair the country’s public finances, sources said on Saturday. The idea is “under consideration” ahead of Hunt’s announcement of a new budget plan on Thursday, a government source said, speaking on condition of anonymity. Under the plan, first reported by The Times, the levy would be increased to 35% from its current rate of 25%. It would also apply to electricity generators and run until 2028 instea…