By Yoruk Bahceli and Nell Mackenzie LONDON (Reuters) – British Prime Minister Liz Truss and new finance minister Jeremy Hunt will have to do a lot more than Friday’s U-turn on corporation tax to restore Britain’s credibility with financial markets after three bruising weeks. Truss and Hunt, a former foreign minister, will be looking to Oct. 31 – the date of the government’s medium-term budget plan announcement – as a moment to win back the trust of investors. The pound and British government bond prices rose on Thursday and Friday in anticipation of the policy shift, but they retreated after T…