OK, The only other thing I can think is to try David Leadbetters famous "stepping" drill.

Address the ball properly, and when you swing back, actually stand only on your lright, then when you transfer your weight to the left, stand completely on your left foot.

Its a fairly simple excersie to get the hang of as long as you don't worry about how far you hit the ball. It'll soon give you an appreciation of full weight transferance with absolutely no possibility of leaving weight on you left hand side in the back swing.