LONDON (Reuters) -A windfall tax on energy companies would not change BP’s 18 billion pound ($22 billion) investment plans in Britain to 2030, although fiscal instability would be disruptive in the longer term, Chief Executive Bernard Looney said on Thursday. Britain’s Conservative government has rejected calls by the opposition Labour Party to levy a windfall tax on energy companies that have benefited from high oil and gas prices, saying such a tax would deter investment. “Our 18 billion pound plans are not somehow contingent on whether or not there is a windfall tax,” Looney said at an annu…