I reckon you're right Clarky. I was a bit worried when I saw the difference in voltage between idling and revving on my Commander and from what I saw on my wife's car, it seems to match what you are saying (very slight voltage change between idling and revving).
I took it in to Battery World this morning for a load test. My battery is rated at 800CCA and the load test showed only 560CCA, which indicates she's stuffed. Plus, the guy pointed out that my battery had been leaking a bit of acid and echoed ren0vator's comments about lead acid batteries not handling the rough roads and high temperatures up here all that well.
I also got the BW guy to check the alternator output whilst he had the load tester connected. This morning it was hovering around the 13.4-13.5V mark at idle and the guy said it jumped up to around 14V when I revved it up. Based on this I reckon that the alternator is on its way out also.
I have found an Optima D27M Blue Top in Perth for a steal that I will grab when down there. I might also have to grab another alternator from a wrecker unless someone knows where I can get a new one from that doesn't cost me another mortgage! Anyone had one of these alternators reconditioned? Surely the costs to recondition one can't be prohibitive?