Looks like I've been thrown a curved ball by a cousin, in the form of a family photo of my grandfather's car. I think I've identified it as a Renault GS (might be an NN) from the early 1920s, Mam reckons the photo dates from 1929. It shows my grandfather in the drivers seat, a mechanic friend in the passenger seat, my grandmother and uncle drivers side rear, and my mother passenger side rear.
Need to get on with the Morgan so I can advance this one to the second build, and hopefully finish it while Mam's still around. It's a prime candidate for the Stevenson build method, as it's mainly flat panels.
Edit: After more research it seems it's more likely to be a KJ or NN model.