HSBC and Standard Chartered are looking at the viability of quitting London for a new home in Asia because a big jump in a tax on UK banks makes staying in Britain increasingly painful. Several investors told Reuters they want the two banks to do a thorough analysis on whether it makes sense to move after Britain raised the bank tax by a third last month. Some are expected to quiz bosses on it at shareholder meetings, including at an investor gathering in Hong Kong on Monday.