The gloomy trading update from Marks & Spencer yesterday (2 July) sent its share price plunging and shudders through the UK retail sector. With food sales falling by more than 4%, the head of its food business leaving the company and concerns over how an upmarket food retailer can appeal to ever-more price-conscious consumers, analysts have had their say on the outlook for the business. Here's a selection of the key quotes from industry watchers.