Yeah the poms call theirs weetabix (not sure how it’s spelt). Dunno where precisely it sits health-wise relative to Vita Brits or Weet-bix.
Honestly I’ve never noticed that much marketing from Weet-bix. The cereal I most associate with sport is Nutrigrain, which is a much more sugary cereal (though not as bad as ones like Cornflakes or Rice Bubbles). I recall Nutrigrain being particularly associated with Iron Man races (the weird surf lifesaving Iron Man, not the triathlon).