James - Sounds like you know what to work on. Here's a bit of a comparison between you and Luke Donald leading into impact.
The Red/Teal lines are the amount of slide generated (address and impact).
The Yellow and Orange lines show the relationship of the shaft and your left arm leading into impact (lag). The thick Orange line is impact for both players. The thick Green line is the shaft after impact (compare this with the position of the arms).
Notice how you are rapidly losing lag here well before the ball. At impact, the club is now leading the left hand, and the hands really decelerate at the bottom of your swing.
Yes, Luke Donald is a pro.... but check out how he maintains lag up until impact. Also notice (center of angle) how he's moving his hands through the ball more aggressively. He's maintained the triangle with the arms, shoulders and club well after impact.
I'd really think about hitting the ball with the back of your left hand as you practice. Accelerate the hands through the hitting area and trust that the club will follow.
If you don't have an impact bag, working with one might really help build lag into your impact position.
Edited by delav - 3/11/11 at 7:29pm