We had a great time looking at the stone and associated products, and many thanks to Giles Heap for his time and knowledge.
The one product that I was really taken with was the exterior grade porcelain tiling, which comes in ten colours - eight stone and two wood. It really looks similar to the real thing, but has good grip and strength as well as very low water absorption rates. I wish I'd been able to use it on north facing jobs before now, where despite best efforts stone always eventually turns green. I've got a feeling I'll be using it before long.