What, specifically, are you concerned about in their proposals?have a listen at what they propose doing this time if they get into power and you might change your mind. i would the shinners in every time over the greens.
I don't think we should ban oil and gas exploration and I don't think reducing the pupil-teacher ratio is a good use of public money as it is probably the most expensive thing you can do in education and has been shown to have limited positive outcomes but other than that I'm in favour of 8 of the 10 headline points in their manifesto.
Paying farmers to protect the environment rather than our current policy of paying them to wreck it is, in my mind, a good idea. More public transport is a good idea. More renewable energy production is a good idea, although ignoring Nuclear is stupid and just bad science.
Details here.
Of course they will only ever be a minority party in government so any crazy stull, and probably most of the good stuff, will be ignored.