To collect water, you can get a large sheet of plastic, make a small hole in the centre. Then put up 4 posts (posts just taller than your water butt) in a square and tie the ends to the plastic, ensuring that the centre dips down. Put the butt underneath the hole in the centre. Rain will collect on the plastic sheeting and run down into the butt.
I have no lid for my water butt, but keep the muck out with a sort of filter, in this fashion:
Take a square of chicken wire about a foot larger all around than the top of the butt. Take a square of fabric (I used weed control fabric, the flimsy type, but net curtain would do). Place the fabric on top of the chicken wire and fold over the sides of the chicken wire to secure the fabric, making a square just a couple of inches bigger than the top of the water butt. Place the mesh ontop of the water butt and scrunch the wire around the top to make it fit closely. I put half a brick in the centre, to stop it blowing off in high winds, and this also makes a depression in the filter which allows water to run into the butt.