Now that the system was starting to stabilise, I could look at other power optimisation approaches, since the unit was still taking more than 700ma, most of which goes on the Pi, the wifi adapter and the webcam.
As luck would have it, I was reading an article about the Raspberry Pi and power reduction techniques for that, one of them was to replace the old, linear regulator on the board with more modern and more efficient switching regulators, this invalidated the warranty, but it reduced the power consumption and by doing so, also reduced the heat output, since the wasted power was released as heat.
I had never even considered using anything except 78 series regulators in my projects, since they were, well, just regulators after all. After spending a bit more time reading up, I ordered some LM2596 switching regulators from e-bay with a view of changing all of them out. Once the arrived, the 78 series linear regulators were removed and the switching regulators went in. Luckily, the previous vertical mounting hack to overcome the Arduino placement on the main board worked to my advantage, I now had plenty of space to place the regulators on the rear heat sink and the wire lengths were significantly reduced when compared the old regulators at the top of the Aluminium heat sink plate, which will reduce noise.
After fitting, I powered up again and the power consumption was reduced by more than 150ma, result !. Less power consumption means a longer run time.