There's something outrageously vulgar even about Trump's appearance that I don't think would 'play' in the UK. The doctored hair. He looks like a Harry Enfield/Paul Whitehouse version of a politician or investment banker from the 80's.
Obviously you can't generalise about an entire culture, especially one as huge as the U.S.'s, but I think there's more of a taste for brashness ''over there''. Our nearest equivalent to Trump (in terms of a political 'personality') is probably Boris Johnson, who is also brash but in a very British way: self-effacing, ostensibly bumbling and clumsy, liable to drop a baby before he can kiss it on the campaign trail.
To carry on with the stereotypes - as a culture I think the British rather despise self-aggrandisement. We're eager to knock anybody who gets big for their boots off their perch. Also, there's this lingering respect for ''class'' - not in the sense of social standing, necessarily, but in terms of ''civil'' behaviour. Whereas in the U.S. I get the impression that there's a lot more value placed on success (/money).
Saying all this, it's not as if British people aren't fascinated by Trump (and by American culture in general, obv.). He makes good TV, because he's despicable. I just don't think he'd have any credibility as a politician here. He hasn't really in the U.S., though, has he? He's like a sideshow to the main event of the election, and unfortunately has helped make Jeb Bush, e.g., look like the sensible option.