If you are going to try to term parties as left or right wing, you'd think there would be some effort to put the right wing parties on the right, and the left wing parties on the left. As I say, if not, these charts are meaningless.
Indeed, and the right-wing parties
are right of centre, and the left-wing parties
are left of centre. However, when you add a second axis to give a more expressive representation of political views, some factors that would formerly have contributed to an extreme left-right positioning get transmuted to an extreme up-down positioning, such that the relative positions of parties on the left-right scale may change. You will notice that, although the BNP's leaning towards the right is fairly diminutive, they are very extremely authoritarian (moreso than any of the other parties), suggesting that the reasons for their classification as a "far-right" party are mainly social rather than economic.
Now, I'm not familiar enough with British politics to state definitively that this positioning is accurate. However, I
can tell you that you can't expect a broad categorisation made using a one-dimensional political spectrum to apply on a two-dimensional extension. If you want to criticise their left-right positioning on the political compass, you're going to have to point to specific
economic policies that support a free market, rather than citing a vague statement of their position on some other political scale.
I don't know what makes this particularly difficult for you to grasp, but please try to think before you type. I'm getting bored of explaining the obvious to you.