Thanks for your reply, Neil. What bothers me about the HP Photo Matte is that I can't state its permanence - which must be an issue when trying to sell prints. 200+ years sounds more convincing than 'a long time'! I have a tiny sample of the Pro Satin, and based on what you've said, it looks like that might well be the way to go. I think I prefer matte, but that has to be second to getting the tonal range that I'm looking for. And once it's behind glass, surface is less an issue for me.
I really appreciate your reply.
Chris.