One minor concern is that I rushed a little too much and they don't meet neatly at the corner. Hopefully with a dozen or more of these there'll be some that fit others better but for gaming purposes we can live with this.
The last shot was after I undercoated the fences black. I thought this would stick to the granny grating a little better but I think it uses far to much spray to fully cover the sand and the rockcrete posts still come out as plastic so I'll be adding a coating of black art paint, PVA for adhesion and some plaster [my usual base]. This will probably be thinned on the fencing because it's chunky enough as it is.
Before I do any more painting I'll be prepping a fair few more fences and some broken ones. I'm confident this test has served it's purpose so there's no stopping me from doing the rest.