No that's not right. You only get one ballot (and that means you only get one vote - but I'm sure you know that
).
1st choice preferences always count so it's impossible for 2nd or 3d preference to achieve 50% on their own (they can only be added to the 1st choice to count)
All you have to remember is that AV is a preference system which simply means the person elected is ALWAYS the person most people prefer.
In practice it's most often the same person that would be elected under FPTP but in cases where that person is not so popular (as in most people don't like him) then it can often be the person that came 2nd in the 1st round that wins. It's actually quite rare for anyone who comes 3rd in the 1st round to win (less than 5% in Australia) contrary to the big fuss the NO campaign made about it.
That's possible under FPTP but very unlikely under AV (remember the winner must be popular with at least 50% of the voters). The idea that the BNP could win easier under AV was an outright lie put about by the NO campaign - and in fact - is the complete opposite of the truth
Obviously any party can win (wouldn't be very democratic otherwise) but they have to be popular with most people to do so.
....and it's this idea that leads to the notion that AV is fairer system
I will agree with you on one thing though. AV is pretty much dead and buried so I don't think there's much to be gained by discussing it.
If we ever do get reform in the country then I think it's almost certainly going to be something PR based :spin:
Best ask Alex Salmond that question