Have you tried your local farming merchant, he will sell strong black plastic, which will last indefinately, and much cheaper. if you keep fish you won't have as much diversity in the pond regarding wildlife as they will eat it up. re pond plants, most garden centres stock them, they are often tucked away in a large pond somewhere, even Maisadour stocks them here, who also stock the black liner. You may not see too many plants like that at the moment as they don't tend to stock them in winter. have you any local streams? ditches? you may find reed etc in them. re the fish, I don't feed mine as that would increase the fertility of the pond, which I don't want.