Ok on the Glencore story
Yes the WFP did buy £50m wheat and other grains from Glencore, one purchase alone was for $22.5m in July at the height of the famine in the Horn of Africa. Not sure what WFP could have done at that time as it had little or no stockpiles of grain and had to buy on the open market. Glencore were in a position to fulfill the order - end of really...
here are some links
http://www.guardian.co.uk/global-development/poverty-matters/2012/feb/07/glencore-wfp-viable-option?newsfeed=true very informative and provides figures on how much WFP money is spent in LDCs
http://www.forbes.com/sites/timworstall/2012/02/07/glencore-hysteria-of-the-day/ a slightly tongue in cheek take on the initial Guardian story
It is worth noting that WFP put all such purchases out to tender and generally buy from those offering the lowest price so as to maximise the amount of food purchased. Generally they would rather purchase from farmers in LDCs as this helps those countries proportionally much more, however in times of humanitarian crisis they must buy quickly and this is where the likes of Glencore and Cargill have a role to play.