A comment -
Not sure if it's the same in the UK, but rather than 'spoil' your votes or refuse to vote, in Australia, if you cross every name off the list (I'll be using a pen rather than the provided pencil), that is a valid vote that has meaning - the meaning is that none of the candidates meet your requirements. A guy called Arthur Chresby looked into this stuff a long time ago.
http://www.tomgrimshaw.com/your%20will%20will%20be%20done.pdf