The boycott a company or two email has been going around for years. For an independant corroboration of this (and comments as to why it's a load of rubbish) have a peek at
http://www.snopes.com/politics/gasoline/gasout.asp It's focused around the American branded emails but it's all the same concept.
It's not the oil companies that are putting the prices up. It's speculation about the cost\price of oil in the future.
http://business.timesonline.co.uk/to...cle3982900.ece Not a brilliant article but explains some of the points and somethign I found quickly trhough google.
If people want to know\learn more about the underlying mechanics of this a good start would be to look up an explanation of "Supply and Demand" economic theory.