It's similar to left-libertarians (a stance closer to mine) have no party which really represents them realistically. While I do support some of the Green parties policies there are many I don't - neither do I have any trust they have the competence to actually achieve many of the goals they laid out. Sadly the party has too many alternative medicine anti-science hippies in it for my personal taste.
What I'd love would be a socially liberal, economically left-wing (strong welfare state) political entity which has a key focus on evidence backed policy, very low on the authoritarian scale with scientific management & long term sustainability as a cornerstone.
You and me both, mate. Instead I'll end up in the position of supporting Ed Miliband's authoritarian centre-right party as the only credible alternative to further ruin wrought by the Tory part.