Back to Chemsley wood though, the turnouts in local elections are so low that there could be hardly anyone who's voted for both, I'd guess there's mostly bnp voters going back to labour and the greens gaining labour voters who never voted bnp
Hmm, I'd understand that if the Greens had never stood before and the Greens suddenly tapped into the Labour vote, but they stood in 2007, with it being a Labour/BNP fight and the Greens on 5%.
Maybe they were disinclined to vote Green and risk the BNP winning in 2007, but with the BNP not looking like a threat, they switched to the Greens.