I'v been meaning to post here how I made our green bean casserole in the end, it was total improvisation as I forgot the Campbell's soup. I fried a little chopped onion and a few chopped mushrooms. When softened, I added a small tub of double cream, plus the cooked beans (fresh green beans, cooked in water for about 20 mins). Put in a casserole dish, topped with crispy onions, bake for 20 mins or so, voila! It was a lot tastier than making it with the soup so I'll be doing this way all the time now.