I am familiar with the website from which that chart comes, and I don't consider it credible. How does it decide where to put the center? It is arbitrary.
I use a non-arbitrary definition: the status quo is center. Anyone who wants modernize authority is a leftist, anyone who wants to diversify authority is a rightist. Anyone who is more of a leftist than Marx is far left, anyone who is more of a rightist than Confucius (the man himself, not his disciples) is far right.
You are correct that Obama and Romney seem to fall pretty close to each other on a left-right spectrum, but the truth is that they are on the left. This is because they both want to move the status quo to the left. That is indisputable. We know that Obama's policies are far left because of his actions on the lumpenprole (people that Marx did not care about). Romney could have gone pretty far left when he was governor of Massachusetts, but he didn't. So we can conclude that he (like most Mormons) is only a center leftist.
And I suppose the fact that by doing that, you get to move the goalposts every few years and redefine where the centre lies is just a fortunate coincidence? No thanks. If governance takes a sudden swing to the right, you can't just turn around and say "actually that's the new centre now" and anyone who's left of the old centre somehow just got more extremist even though their views haven't changed. Nice try, though.
As for it being "nice" to see UKIP do well, I'll have to disagree. Scapegoating minorities and blaming them for all your economic problems is the kind of backwards thinking that we, as a species, should have been able to move past by now. That sort of BS should have ended with WW2. UKIP are disgusting, vile creatures.
None of the top three parties addresses any of the concerns of the average person. UKIP not only addresses them, but has decent solutions. Also "move past by now"? Do you see the demographic shifts that are happening around you? How many children does the average Labour supporter have? How many does the average UKIP have? I'm guessing that the latter is at least twice the former. In the US it will only be a couple of generations before we shed the progressives. They'll be a few of inconsequential weirdos instead of the ruling class.
Their concerns are simply misplaced. People buying into a farcical fear campaign because they're gullible and afraid doesn't make their views justified or in any way realistic. If anyone voted UKIP because they genuinely believe people who have committed no other crime than being born within different arbitrarily drawn lines on the map will somehow destroy the country by coming here, then I'm sorry, but I think they've been manipulated. Having less people coming from abroad won't miraculously fix any problems, so actually, no, UKIP don't have any "decent solutions". Anyone who thinks it will change anything for the better is, quite frankly, broken in the head and in denial about the fact that their view boils down to the simple fact that they're scared of the boogeyman and the current boogeyman of choice is foreign people. It's pathetic.