So not long after writing yesterdays post I came to the conclusion that the cobbles definitely were not right. I'd gone for a very random cobblestone look, but this really doesn't work when the cobbles are all the same size as you can't place them randomly without them either overlapping or with large gaps between them. So I've started experiment number two.
borrowed from Chris Nevard, but this time I've placed the stones in a regular pattern and I think this looks an awful lot better. One thing I like is that it isn't perfect. I could probably do this with some embossed plastic sheet but I think it would always look too regular. Hopefully this version, once painted, will work and be regular enough to be convincing but not so perfect as to look modelled.