In the spirit of the OP, it would be individual actors or comedians, not a troupe.
Could we then count just, say, John Cleese?
I’m not the OP, but I’d say “put 'em here and let’s see.” I should point out that I’m in my late thirties, lived in Britain for a decade, and aside from “And now for something completely different” I couldn’t tell you one single Pythonism. I know he had a few lines from Fawlty Towers.
If we’re talking British comedians and catchphrases, I’d go with Kenny Everett (“And it’s all done in the best possible taste” and many others), Harry Enfield (Stavros), or any of the major players on The Fast Show - probably Paul Whitehouse.