Very good and fair analysis from the BBC's Nick Robinson...well worth taking the trouble to read !
http://www.bbc.co.uk/news/uk-politics-29571412
Some key words ::
"At the last general election the Greens got an MP elected in Brighton with 1% of the vote nationally whereas UKIP got none with three times as many votes.
At the next election UKIP could beat the Lib Dems in the national vote share but get a fraction of the number of MPs.
Until recently the optimists in UKIP talked of them electing a handful of MPs - Farage certainly, maybe Carswell again plus one or two more. With that level of support they'd be very unlikely to hold the balance of power. Mr Farage will not get to be Minister for Europe. The self styled People's Army would not breach the walls of power "
So, simple arithmetic may win in the end it would seem.