Hi Andy,
Sorry to hear you're under the weather (is it literally weather-related?), hope things improve soon.
Like Gael, I'm sure many of us enjoyed the "start with the hardest piece first" approach!
Other upholstery problems I see on many restored cars are the compound curves on each end of the dash, the 90 degree bend on each end of the soft top cover and the front edges of the door panels. Your techniques really seem to work though, the horn pad and instrument pod certainly look good.
I believe that 10mm strip of dense foam on your car is probably original and it looks good enough to stay there. I don't think the thin foam sheet continues over that dense foam strip (or the A-pillar covers) but I'm not sure because, as you know, the thin foam degrades to almost nothing even in places where it originally was installed, like the dash top. Alfred or Achim may know.
IMO the ultimate period-correct antenna for your car is the Hirschmann automatic 6000D58 - see photos. This is one solid piece of work weighing around 3kg. Seeing as the antenna is completely hidden in the front fender though, I guess you would be fine installing later model. Or a manual version but I can't help thinking that sooner or later someone would bend it!