The market is highly concentrated, dominated by the Kellogg Co. of Great Britain, Weetabix Ltd, Cereal Partners UK and Quaker Oats Ltd. Kellogg holds the major share, around 42% of total market volume, while Weetabix, Cereal Partners and Quaker together hold 31%.
Taken from
http://www.the-list.co.uk/acatalog/kn15155.html