So, what a difference that made!
After changing the angle on Sunday, we had a couple of fairly cloudy days, so there was no opportunity to see what a difference it had made. That was until today.
Today was the first really sunny day we have had since the adjustment and it's made all the difference in the world! Below are images from my monitoring station from Sunday and today. As you can see the panel voltage is much higher starting around 1130-1200 Sunday (when I made the change) and today, the battery is steady at almost 15v and the panel is giving pretty much 20v I am assuming that this means the controller has detected that the battery is full and has put it on float charge. This is the first time I have seen this behaviour.
I am so impressed by this, I am in the process of designing a solar tracking system to help even more. There will be more on that in the future, but I have ordered motors and an accelerometer on ebay and while I am waiting for them to show up, I will be designing a circuit and starting to write the firmware for the tracker.