To me if you bounce around on the horse's back then you can't ride. There shouldn't be air between you and the saddle except when you want there to be. Using your hands and legs effectively depends on being able to sit/post correctly.
Remember your position is very important with english riding. THere should be a straight line from your shoulder to your hip to your heel. Its a difficult thing though, if you fix one tiny thing of yourself you might find flaw with, you will probably discover there's something else going wrong!