Well its focus is in large part due to a concomitant rise in Islamic encroachment and the perception that the State is either uncaring or on the Islamic side. That and a widespread feeling that they are not represented by the government and don't have a voice. I think the radical Right (such as they are) are also strongly pro-Leave and there's a widespread fear that the government is going to renege on the results of the referendum as well.
Now whether it would find another focus in the absence of Islamic encroachment is a different question. I think in large part it would because when someone wants to plant a bomb it's usually because of problems in their own life rather than someone else's. At least in the developed Western world. However, what would be different is the level of support and emboldening for it. With Islamic terrorism, the problem is not the individual terrorist per se, but when a community is willing to support that person's views and encourage them or look the other way. It's why an unhappy person in one Islamic community will just be an unhappy person. And the same person attending a Wahabist mosque will be someone who learns that talking about killing infidels gets them attention and support. Similar with your "far Right". An unhappy person might want to lash out but they lack the social direction and support. However, as groups that hold hateful views grow in number, they form the muck in which your proto-terrorist can grow and bloom.
Proto-terrorists, well I wont say they're fixed in number independent of all social circumstance because that's not true, but my point is that there are always proto-terrorists and what turns them from that into real terrorists is a supportive, ideological group around them. Now Islamic communities have had such groups increasing significantly for the past twenty years under the backing of various state-level operators. (Saudi and USA, I'm looking at you). Sufficient numbers of "far Right" haven't typically been clustered enough to incubate much in the way of terrorism until recently. But with that rise in Islamic encroachment and feeling that the State either doesn't care or is on the Islamic side, such communities are growing now too. I should add also that it's not simply Islamic encroachment. That is one aspect. It is also very much a feeling that nations are being eroded, governments rendered impotent or corrupt by a globalist agenda. Disenfranchisement is the water that makes terrorism sprout and angry communities provide the dirt.
That is why historically we've had much less terrorism that non-Western countries: because democracy heads it off. People are doubting our democracy right now in ever increasing numbers. As someone elsewhere said, for many people in our FPTP electoral system, Brexit is the first time in their lives that their vote has actually meant something. If faith in democracy fails, Hell will break loose.
