Update:
Although the blades have not arrived yet my Uncle Fred will be doing all the fabrication and assembly for free. He'll be cutting out a steel plate for the washers (think he mentioned 10mm) to a 32" hole for the hex. He said that this was a better option than PVC pipe for the spacers because it is easier to get the blades square with the steel plate option.
He has also made a template for the (turns out to be 28.4mm hex) which he'll use to guide a carbine tipped grinder to cut the circular 25.4mm bore of the blades to the appropriate hex.
He's going to Tasmania for a holiday for 3 weeks and will start on his return.
I'll post some pictures of the process when that happens.
Guessing I wouldn't need to use the groomer till about late October as the lawn will be scarified and aerated on 3rd September and hence will need time to grow through the sand top dress to fill in the cores and level up the low parts of the area.
