Would really recommend Top Barks' whistle training for recall. It takes some work, but it is fun at the same time, and very effective. You do need a really high value treat that is only used for this - for Jess it is tiny pieces of cheese, she never has this at any other time.
We walk her over the fields and she disappears off into the woods but comes zooming back like a little rocket when she hears the whistle.
Don't let Bobby off the long line until you would bet your mortgage on him coming back - the thing is not to let them fail.