I appreciate your sentiment but just what is the right choice with relation to Mr. Cameron?
Vote for Labour, who in previous incarnations were responsible for some of the most shockingly illiberal policies and erosion of human rights we've ever seen, such as Regulation of Investigatory Powers Act, suppressing of Chilcot enquiry, collusion with the US over weapons of mass destruction in Iraq, the list goes on?
Vote for UKIP, who are outright fascist, misogynist, racist, homophobic bigots?
Vote for the Liberal Democrats, whose entire existence is supposed to be a moderating influence of the Conservatives yet their coalition seems to be turning out pretty right wing to me (see above).
After discarding these choices you are left with minority parties. The Green Party actually gets more of the vote than UKIP, but a lot less of the media attention. Great, but sadly the Greens are completely deluded when it comes to the realities of our energy policy and would have us moving away from nuclear and wasting money on renewables that don't make sense for the UK. They have nearly as many crackpot candidates as UKIP, the best thing you can say is at least the Green crackpots believe in crystal healing and muesli knitting as opposed to white supremacy.
In reality whatever party is in control next it is going to be exactly the same issues; the same civil servants who want the power to snoop on communications now will be whispering in the ears of the new administration and getting them to try to pass the same bills. Voting "not Conservative" isn't going to help avoid this.
I have no idea who I should vote for, or who any other person in the UK should vote for. The root problem seems to be that as constituents we don't really care about civil liberties. The average person in the street will be simultaneously happy for the security services to have access to all communications but also wish for the nebulous concept of "privacy". Therefore why expect our elected representatives to care either?
It is thoroughly disheartening but perhaps it is education of the masses that is continually needed.