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.

Hi mluh You've obviously done your research on these products, so it's most likely going to come down to personal preference. As you've mentioned, a natural stone is going to come with an amount of maintenance but the beauty of Travertine is within its variation. Once sealed with a good quality sealer (I recommend Guard Industry), the maintenance is really quite low and most spills are lost within those natural variations. 99% of spills can be cleaned up without too much trouble. Porcelain, on the other hand, can be quite difficult to clean once it's been marked. That said, the external porcelains have a great non-slip texture and are very hardy when used as paving/tiles. I'm personally not a fan of using them as pool coping, but many people love it. Again, both have their advantages and disadvantages so I would recommend using the product that you're happy looking at for the next 10-20 years. - Jordan

Thanks for that Kate. Yes I’ve seen this video already actually :) However it doesn’t explain if need wet concrete at same time under each paver before placing it down and haunching (as my pavers will have 50mm spacing between them so it’s different to the one in that video which are all continuous / butted up against each other).