I go to the local farm shop but its only a 15 min drive for me. I've bought a plastic dustbin and put them in there. So far the mice haven't nibbled through but if they were just in the bag I'd be feeding the mice as well for sure.
I pay about a fiver a bag for grain and a little more if I get pellets and mix it all in a big bin with a clip lid. Keep them in the sack and you'll get mice - I wouldn't even do that in my house. But then I have a holey old house .
Is there not a feed merchant or farmers coop nearer to you?
I use a large kitchen pedal bin, a metal one, it works fine for the chicken feed and is neat enough to just tuck in the corner of the quite large chicken shed we have. I have to say I get my feed from the local saddlery, they order in organic for me, so £10 to £12 per bag, depending on layers or growers.