Just a quick look at your spread sheet Clive but it seeems dynamically flawed in that the figures quoted are for a saving based on these figures when in effect it is a loss.
To incurr the gains you are elluding to you would need to be home during the daylight hours and use all he energy generated.
Column D of the spread sheet is the cost to purchase electricity, while the feed in tarrif is a static gazetted figure with no room to move in any direction other than down. The NSW Gov has made an effort to retrospectively reduce the the feed in tarrif for all customers but at least fell on the sword and elected to keep it as was for existing customers.
With feed in tarrifs equalling or below the purchase price of retail electricity the only saving equal to the retail price is by using the power as it is generated.
Any other method shows a reduction of return when based against a rising electricity market.
The figures I quoted for SA is based on
http://www.silexsolar.com/documents/CEC_booklet_1.pdf This possibly does include the losses for tilt and trim. It does assume all systems are the same and this is not the case as a can be shown when testing systems and losses based on individual location etc.