Retrochic....15% isn't "many" as someone has suggested on here today, and UKIP know that. They are in the same position that all minor parties are in a essentially two-party system like Britain. Look at the Electoral Calculus wedsite ::
http://electoralcalculus.co.uk/homepage.html. Support for UKIP doesn't mean seats in Parliament and its seats that win elections. The Liberal Party and SDP found that out many years ago and Farage will learn his lesson as well.
Important quote from the EC site ::
"However, the new split in British politics is not on the left as it was with Labour and SDP during the 1980s. Rather it is now on the right, between the Conservatives and UKIP. Although UKIP are unlikely to win many seats, they take votes away from the Conservatives and make it harder from them to win a general election"
Its not enough for UKIP to summon up support. In order for UKIP to do well, the Tories have to do badly, because its from the right that UKIP gets most of its support ( and Party activists for that matter )
Just to remind everybody...UKIP only has one policy and its contained within the name of the Party. If people really want to come out of the EU, then a vote for UKIP is going to be a wasted vote.