Many thanks for that Corey, I don't have a problem with either wet moulding or angled box stitching, though to be honest I don't use it unless I have to!
I had thought of trying to rig up a jig to use a router to get the lip but am having difficulty getting hold of thick enough hide to do that in any case. Think I am going to go the easy route and use a quarter inch strip of 4.5mm on a half inch strip, burnished before construction and stitched vertically, then stitch vertically through the half inch strip to the case outer, leaving only one row of stitching visible on the outer....if that makes sense. Not as neat as the one in the photos but it should be presentable, albeit with a thicker "lip".