"While UKIP hasn't yet mustered up any elected members of the UK Parliament...."
They are riding the wave of discomfort with Europe. It's not just Americans that can be insular - we are damned suspicious of foreigners too - and we have a lot more of them a lot closer to us.
While our economy is no great shakes, it is better than most of the EU, and local lads losing building contracts to Lithuanians tend to get a tad upset. Me- I'd stop whining and actually do the job for a decent price at the time stated, like the foreign national residents do, but I guess complaining is easier.
In terms of national power, UKIP don't have a snowballs chance in hell. Even the Green party has a Parliamentary seat (Brighton, I think), yet they haven't managed a single one.
The problem is - they sound decent enough on the surface. National sovereignty, gt rid of faceless regulators from Brussels messing with our Political and Judicial system. Noting bad there, right? If you consider the EU as the USA and the individual nations as states, it's pretty much pure 10th Amendment.
The baggage they bring with them though is not. UKIP is the polite face of the National Front - a white supremacy group that makes the dicks over on Stormfront look like models of tolerance.