I started by painting the paving with a concrete coloured acrylic, which I thought too light and added Lifecolour dirty black. This seemed a better colour so I brushed it with charcoal coloured weathering powders to bring out the paving stones. This almost turned out to be a disaster though, as contrary to previous experiences with weathering powders it stuck to the pavement like you know what to a shovel. Perhaps the paint was still slightly tacky. I wiped most of the powder from the flat surfaces with a damp tissue and dry brushed with the original concrete paint to highlight everything. Finally a coat of Testors matt varnish was added to seal everything in. Testors is the best matt varnish you can use but rumour has it that it is no longer available either here or in the States where it is manufactured.
So to recap, I started with a colour I didn't think looked right, then after repainting added powders that made it way too dark, which then turned out great after wiping down and dry brushing. Moral of the story is; persevere. We often read magazines where the experts seem to know exactly what colours to use and they probably do but that's only after years of experience getting it wrong and experimenting. Don't be frightened of having a go.