It is certainly true that a large number of people don't vote Green because their vote will end up in the bin. We will only find out how many if we make the change to AV.
Other parties only get our second preference votes if we put them second.
I am sure that there are many who would put green then tory as well as those who would put green then labour. There are even voters out there who would put BNP then labour.
I am disappointed GiddyPickle that after all the research you have obviously done you are rolling out the "small party holds balance of power and decides who wins". You know very well it doesn't work like that. If a bunch of voters put party E first then party B, and E is redistributed causing B to overtake A, that is good and the whole point of AV. Instead of the E+B vote being split allowing A in with possibly well under 50% of the vote which happens in FPTP, B gets in.
I have yet to see an example where FPTP gives a fairer result than AV.
You've rolled out the claim of tactical voting again when everybody else agrees that there will be less tactical voting under AV - the only example I could find on the whole internet where tactical voting would get a better outcome for someone was one where you have to know everybody else's vote to make that decision.
Very safe seats will always be very safe seats - there is nothing unfair about that.
Most people believe AV will increase turnout.
The one real issue you have raised is that of more spoiled papers: I sincerely hope that if AV happens that papers with a single X in a box will be treated as a first preference for that party and that other such sensible judgements are allowed - e.g. a 1 and two 2's - the 1 is allowed to count and the paper only treated as spoilt if that party is redistributed.
But I think the number of people who can't write 1,2,3,... is small enough to make this a change worth having.
No it isn't PR - but it is the fairest way of electing a single constituency MP, so we should use it.