I object very strongly to the categorisation of the BNP as “far right.” The party is not on the economic right at all, they are to the left of Labour, the Tories and the Lib Dems. But their economic policy is not what we measure them on; fundamentally they are nationalist, and that is what defines their politics. This is clear by reading any of their policy in detail; they even blame Climate Change on immigration. Political Compass measures party policy on two axes; both economic left and right, and authoritarian/libertarian up and down, and makes the mistake of saying that the BNP mark themselves out on their authoritarianism (while they are in the same ballpark as the Labour party at the end of a stint in office in that respect).
The nationalism/internationalism axis is orthogonal to both the Political Compass axes; and should not be confused with either of the others. Utilitarian (and arguably world-communist) internationalists want to bring the world under one supreme authority to ensure the supreme efficiency (or equality) of all peoples, while globalist capitalists want to bring about giant international free markets, and like the utilitarians argue that this will maximise efficiency.
On the other side, nationalist capitalists (like UKIP) want to pull up the drawbridge: limited international trade but no movement of peoples (a quite upside-down way of looking at economics, truth be told,) and in the former Soviet Union (and still in North Korea) there were/are totalitarian restrictions ensuring that only communist produced goods are consumed, and restricting any emigration. The BNP are somewhere in the middle, favouring free markets inside the walls but nothing going in and out, while being the most extreme on the nationalist axis.
So you see, the left and the right can both be internationalist — it is only the nationalists who can’t, regardless of their positions on other axes. My personal politics as a social liberal is what informs my internationalism; I seek equality of (measurable) freedoms, and there is no philosophical justification for splitting any population up into sections that deserve those freedoms and sections that don’t. I am internationalist because I believe in a philosophical equality of all persons, and I can find common ground with most of those who I disagree with on this basis.
As such, the argument to be had is not between the left and right here. People on all sides have and do oppose members of their own economic “team” when it comes to internationalism, and that is why all* can eventually be persuaded to the internationalist cause.
* apart from the nationalists, who believe in a fundamental inequality based on peices of paper or parents…

