Grahame, I really like the lift you have given to this image. I must admit that when I read your explanation that what you have done here is somewhat above my pp skills at this point. You can be sure that I am going to work through your explanation step by step to see how it works though
You mentioned a luminosity adjustment, I know there is a luminosity blend mode but I don't know of the adjustment. Is the luminosity blend mode and adjustment the same thing? (it's ok you can laugh yourself silly if this sounds odd) I am using/learning photoshop cc.