Sir Michael Bishop, the former boss of airline BMI, has joined the lengthening list of people who do not want the chairman's job at ITV, but that has not stopped broker Goldman Sachs from advising its clients to buy shares in the company.Goldman Sachs has upgraded its recommendation on the terrestrial broadcaster from 'neutral' to 'buy' despite the turmoil at the top at ITV, which is also on the look-out for a new chief executive officer. The US bank expects a 'modestly stronger-than-expected recovery' in television advertising revenues in the third and fourth quarters, with relative performance helped by weak comparative figures from the second half of 2008.Goldman has also seen signs of advertisers booking slots at late notice, which should give a boost to ITV. The broadcaster's share price has underperformed the market, Goldman notes, and by the US bank's calculations there is the potential for the share price to rise by as much as 25% from here.