I'm a sucker for the neatness of the square.

That looks like it. Some call it crazy paving. It usually gets laid over compacted paving sand/s. The joins between each flagstone are usually concrete with the edges concreted so it stays in place. I have seen some with sand between the joins which also looks good. New sandstone from Gosford Quarries looks superb but is expensive. (its a great product!). I'd look for some second hand stuff on Ebay/Gumtree/etc.

I checked the pavers that were left over from the same batch...low and behold 2 out of the 13 pavers also had the same white streaks on them. These are unused pavers. I'm now leaning towards the manufacturing stage and the retailer I have convinced of the same. He is sending someone out on Monday to see if some sort of chemical will clean them. I fear the worse but let's see how it goes on a couple of them. I agree with you all entirely, the streaks and scratches should have been seen before laying and not used. Luck is what I need for Monday, failing that, block your ears as I ask the pool renovator to pull up the defective pavers and lay new ones.... Renovating tests your body, mind and spirit sometimes lol

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