I mean, I don't think there's room to argue the "actively known for" claim. British food is absolutely known for being bland, fatty, and overcooked (at least in America); it's even the punchline in that "in hell the cooks are British" joke.
As for whether its true, that's a much harder sell. I can buy that Britain has quite a bit of bad food; 'British' mass-market food can be a bit shoddy, since it tends to be traditional dishes like fish'n'chips and pies that respond terribly to low-quality ingredients and lengthy storage. The restaurant stuff is much better, but it can certainly seem rich and heavy to those unfamiliar (partly because it's special-occasion food being served every night).
But to sincerely claim that the Brits don't have good food is a bit absurd. It seems to be born of either ignorance or ahistoricism. People know "fatty pies", but not cullen skink or any of the other more specialized delicacies, and they seem to have gotten their sense of what's available in around 1945, which was understandably not a high point in British cuisine.