Thanks for all that. I still have a huge pile of reference material to wade through but I think I'm beginning to understand what works and what doesn't.

Horns would, I think work best in corners and I only have one decent corner in my living room. In this house, I will stick with the Castles. I will continue to study alternatives in the hope that when I move house, I will be able to do something better. (At the very least I will make sure I have a suitable wall and room shape for the little Dynaudios to work properly).