First off, I think you're on the money to wait and see. Nice one. But I think the reason the UKIP have focussed on immigration is that it's a touchstone word with several quick buzzwords to float around it, all of which can whip up quick pockets of support. I think they know it's a good 'seducer' so-to-speak, and it will be interesting to see what they can offer in terms of policy beyond buzzwords and phrases.
I think that blaming immigration solely for the issue at hand currently is far too easy, I really do. It's a lot more complex and actually revolves around what people are prepared to do for each other, what people are prepared to pay, whether people are prepared to acknowledge that public education has been **** for 15 years and whether corporations will ever sacrifice a % of their profit margins in order to help regenerate the parts of the UK which have been killed by cheap labour, de-investment and the rampant 'me' culture. All IMO...