On the subject of shading I discovered, after posting the above, that the Passivhaus Component database has a category for “Sun protection systems”.
Having checked out the options I see that none are suitable for my house.
All makes and models appear to be for inward opening windows and are fitted between window head and lintel. In other words, you need to replace your windows at the same time as fitting the shutters.
My own take is that they would be fine for sash windows too, just not outward opening.