I can't disagree too much with the 'like' interpertation, I think this is dependent upon your view of how useful a single vote can be and the myriad of issues that can impact on the realisation of a 'useful' vote.
I think that's irrelevant because a spoiled ballot paper isn't a vote.
Spoiled papers are not ignored, especially if it becomes a larger problem, they may not impact on the outcome directly but when they hit a certain percentage of the total vote it starts to undermine the democratic outcome.
How? Since they just go in the bin, how do they make a difference?
I've just looked for details on the voter turnount in the UK (it's higher than I expected, so I've binned the point I was going to make) and the first hit makes my point pretty well:
http://www.ukpolitical.info/Turnout45.htm
The chart below shows the percentage of registered voters who actually voted at each general election from 1945–2010, excluding votes deliberately or accidentally spoiled.
A spoiled vote isn't a vote. It's just a slight waste of paper.
Spoiling a paper - specifically in a determined campaign - is better than not taking part at all.
Why? Either way, it's a person choosing to not vote. While a low voter turnout could be considered to undermine the democratic process, the details of what the non-voters do instead of voting are scarcely relevant.
Change. The sort of change you, yourself, seek.
It would be merely transient publicity for the fact that a non-trivial minority of people are dissatisfied with both parties and that's neither news nor a change.
I'm not so willing to assume that England will remain Right wing indefinately.
Something will eventually pull the middle ground of politics more the the centre of the spectrum.
I think the whole idea of right and left is an over-simplification and any minor changes to where someone would put the government on that model (and different people would put the same government in different positions anyway) would make no difference. Even the extremes end up being much the same to people in general.