I know at least one person (and have heard of one more) who said they were wavering between UKIP and Green, which took me a while to process but I think I understand now. (Not agree with, but comprehend.) I think it's that UKIP has successfully sold itself as the working-class anti-establishment vote - both of which, for the record, I think are good things, but not when they're coupled with racism and fascism. UKIP is collecting voters who are frustrated with how small the difference seems between two big pro-austerity parties mostly made up of people who went to Oxbridge and immediately went into political jobs. I think it's possible a lot of those people would have voted Lib Dem before, but not after the experience of the coalition government.