Andy Burnham will have a lot of important jobs when he steps into Number 10. One of them will be to try to fix the UK’s apparently broken stock market.The persistent undervaluation of UK stocks may provide buying opportunities for investors, but it seems to be overseas institutions that are taking advantage, rather than the country’s own DIY investors.EasyJet (LON:EZJ) is the latest British company to be the subject of an opportunistic takeover bid from a foreign private equity firm.