"What I wanna say is that I'm a keen advocate of accountability, transparency and information sharing for the purpose of improvement and positive challenge, and the extention of this to parents through my role as their representative on the Board."
IMVHO that isn't going to get you elected. It sounds confrontational and focuses on the parents, rather than the children.
Take those (very useful) sentiments and change them into child-friendly language.
So: Accountability - You may want accountability to the parents, but there are frameworks for that (however rubbish) through Ofsted, etc. So change that into a sentence or two about your passion to ensure that every child has access to high quality teaching and reaches their potential.
Transparency - Again, the school doesn't have to be transparent with parents. They are allowed to withhold some aspects of their work and share what they deem necessary, within reason. So change it to something to do with fostering good communications between parents and the school.
Information sharing - fair enough, bearing in mind my comment.
Generally, the parents are going to want to see that you want to be a Governor for the good of the children and the school, not to use the position to further an individual agenda.
Whether the role depresses you will probably very much depend on the following:
-How 'good' your school is to start with.
-How flexible and collaborative the HT is, and the overall relationship with the GB.
-How good your Chair of Governors is at leading the GB
-Whether you can make peace with the strategic role of the Governing Body and leave Operational matters at the door, or at least make sure that anything operational you want to bring up is phrased as a strategic matter 