Can I make a political point?
If you think your party of choice has no chance of winning, voting for a different party just to stop another getting in is almost as bad as not voting at all. People are often so caught up in what they don't want they won't vote for what they do want. Basically, as long as the perceived enemy doesn't get in all is well.
We should also ban political opinion polls, at least during the electioneering period. All they do is influence the way the public votes rather than reflect true public opinion. You don't have to look at an opinion poll graph for long to reach the conclusion that a vote for the LibDems or one of the 'others' is probably a wasted vote. The problem is that in reaching that conclusion it is not based on party policy but on data from a newspaper survey.
How many voters will be voting Tory or Labour just to prevent the other gaining power? The vast majority I suspect. It is voting for the lesser of two evils when they should really be following their heart whether it be LibDem, UKIP, Green or whoever.
I find the whole election process interesting but I do wonder how much really changes with a change of government. Alf Garnett was pretty close to the mark when he said: "I've served under fourteen Prime Ministers, and been poor under every single one of them!"