Is it really still the case (if it ever was) that Brits don't like winners? I think it just comes down to personality. As you said (Shamrock) -winners normally share an unwavering win mentality, arrogance, that doesn't make them appeal, which is probably the reason people don't want to celebrate their success.

Eubank played the role of villian. Naz was as equally liked as disliked, wasn't he?

Did people really love Bruno more because of his defeats?

Lennox Lewis had an "American" accent and was the opposite of Bruno personality wise.

Hatton was a win machine "everyone" loved. He seems to have lost fans since his defeat.