70% really? only 34% of the voting population actually voted
in the euro elections and ukip the main anti europe/immigration
party won around 30% of the 34% that voted.
The polls cite 70% concerned with immigration, not me. As you point out only 34% could be bothered to vote.
You cannot further extrapolate the figures to find out who is frothing at the mouth, not even on a turn out of the elections. Although a quick maths tells me that Labour, Conservative and Lib Dem voters must as a matter of course be concerned about immigration (which is not in their manifesto's). As of course there are Labour voters(etc) with immigration concerns who have not voted UKIP so a comparison would not hold true. And of course "immigration concerns", cover illegal immigration, legal immigration.
so if you go by what happened at the eu elections around
10% of the voting population are frothing at the mouth and the rest
are full of apathy and disinterest.
Its hard to quantify "voting population" given the rise of postal votes in "certain" areas

And areas where there has been acusations of vote rigging. You seem an educated man Gary, would you care to profile a candidate who is likley to be at the recieving end of "vote rigging" in the UK ? Or shall i do it for you?