I think the cereal is more Swiss / German than British, but I do recall an episode where Glenda mentions Barry eating muesli / mueslix. Of course Edie frowns and says something like we don't need to know that. Don't know the episode. Maybe this helps spur the thought of the answer for the question posed.
When the question was first posted I thought of Edie and Wesley. Edie called Wesley inside to make sure that it was him as he ate his 'Sugar coated Popsicles' behind his newspaper. I know in one episode that Foggy mentioned Shredded Wheat but I can't remember the episode. It was in relation to Compo's trousers if I recall correctly.