Coils for vertical axis wind generator (VAWT)

I've followed several instructables concerning vertical wind generators but found it hard to locate magnets of any decent size here in the UK. I'm going to have to order some that are about the size of a 2 penny piece (the cost of anything bigger is much more than I can pay for)and therefore I will have to make similarly small coils to equal the magnets size.

Considering the base of the generator is 40cm in diam how much space must there be between each coil and can you have more than one row of coils. Another one inside the first. The same configuration with the magnets ofcoarse.

Lastly, on these cicular magnets is there a plus and minus to give you an idea of what way round you should attatch the magnets to the bottom side of the rota.