Jarvis Bay sand is a good filler, if you mix a little cement into the layer the pavers sit on and tamp it down the pavers will follow the contour and sit quite well, draining any surface finish away from the base of your dwelling is a Building Code of Australia requirement , to promote the reasonable and stable moisture content of the foundation material supporting the dwelling , clay is the worst and is likely to react with the variance in moisture content, I see a lot of paving jobs that look like Jarvis Bay on a windy day after a few years of service,, I reckon the barby and beer should be construction requirements, not when the jobs finished, beer and sanger's on the finished job mmmm herbs , another river cottage how about a herb party