Hi Steve
Sorry to hear about your health issues and hope you recover well.
My personal opinion is keep them all 🙂
Seriously though, The Alfa 156 and Herald will only ever go up in value so I would be tempted to keep them and lots of fun to have at shows, etc.
The others, superb as they are, I would let them go if you don't use them much as they will still need maintaining and thats where the costs are (in my opinion).