As for the rest of your post I don't need to tell you what the main driving force behind the far-right surge. It's the fucking EU. Since the far-right is by definition populist they're using people frustration with EU and its idiotic decision making as their main argument. Farage only became popular because of the EU. It wasn't migrants and it wasn't his members' constant fuckups, it's was the EU. He's been feeding of it for years and after a temporary surge because of his "victory" he's eventually gonna starve.
That is not true - I give you the Polish example, where even the Law & Justice party is pro-EU, despite them being UKIP-like in almost any other regard (80% of society would remain in the EU if a similar referendum happened here), including a mechanism which led to their electoral victory - votes of disenfranchised. Of course it has nothing to do with immigration. It has everything to do with governments going for austerity and claiming it is the right solution, everything else is just a scapegoat/distraction (especially the EU). You cannot attempt to castrate public services & education system and expect that people who find those elements the only real state presence in their lives will not notice, especially that it can only lead to even greater inequality, as those with enough money will have access to better paid education/healthcare anyway. If you narrow the resource base, there is always going to be a visible other to blame - immigrants, minorities, "5th column" and so on.
As old protective measures simply won't work anymore (the level of economical interdependence is just not comparable) new solutions of wealth distribution must be implemented, but the collective stupidity of post-08 economic policies gives rather little hope for the current establishment, especially when some would rather point fingers at the framework of European cooperation (again easy scapegoat - institution which people simply know little about), then at the people really responsible for these measures - who, especially in the UK, have been more then happy pointing their fingers in the same direction for years!.
In my opinion, your attitude (blame the EU that is) is sort of symptomatic - EU bashing is the easiest and - seemingly - the least politically expensive solution, whereas the true blame lies with national governments thinking that going only for macroeconomic indicators is all you need in terms of policing - which is obviously BS, as the social cleavage widens faster then the potential economic growth.
According to your logic, basically, were the "Syrian immigrants" the current scapegoat for your public (as they're now in Poland for instance) - they should be the ones to blame, because their very existence fuels support for the far-right.
As for the UKIP's future - they're not going to starve. They, or another project like them will feed off of continued austerity policies, economic uncertainty & slowdown that will ensue for years as the result of Brexit. You see the problem is that they have shown that they are able to construct a narrative that people believe in, it might still include the "Evil EU" as the future deal will not be to everyone's satisfaction. To rule hearts you only need to tell people fables they wish to hear, preferably show them the dragon and yell - charge! It works, you only need infinite supply of dragons & that's an easy task. This is what desperation and lack of perspectives make of electorate, and to combat such populism one has to propose a positive, realistic project of similar attractiveness, moreover, be able to "sell it" - and that's not an easy task.
Which brings me to the last point - I really hope your left will do better than ours (as I said we already have UKIP) - ie will be able to get their shit together, and instead of critically contemplating the reality from the commentator's seat, actually do anything about it. Ours is fighting to even get to the parliament & will probably fail.
EDIT: LOL. I really should stop commenting, I'm spawning barely cohesive essays based on my somewhat limited knowledge of facts on the ground, basically speculating about quite complicated issues I know too little about to make such categorical statementst. Thx for bearing with it though.