[1] is probably the best analysis of the field. Last week on BBC Question Time, the folks on the panel and in the audience all seemed very hostile to limits on freedom of speech - though they noted that those rights are much more robust in the US. Perhaps this is Cameron's attempt to make sure that UKIP doesn't steal away some Conservative votes. UKIP seems most hostile to immigrants, from what I can tell. (I don't live in the UK, so perhaps someone can correct/expand).

[1] http://may2015.com/