Better starting a new thread as this one is 5 years old.
Whereabouts in the country are you? I don't think you need to worry too much about the snakes - I assume they are grass snakes. They do eat fish, plus other prey such as frogs and toads, but they don't eat a very large amount - a fairly small number of prey items will keep them going a whole year. Goldfish are capable of breeding at such a rate that the odd one taken by a snake isn't going to make much a dent in their numbers - nothing compared to the amount a heron can eat.
Grass snakes in any case are not doing terribly well, so it's good where they can survive in gardens. Please be very careful with netting (especially the flexible strawberry net type) which can very easily kill snakes (and other wildlife such as birds and hedgehogs).
Individual snakes will have a home range and will have a poor survival rate if relocated elsewhere, so moving them isn't a good idea.