I’m working with sharpen and blur in Resolve and it looks good. Some of the episodes have too dark parts or the saturation is too high but I leave them mostly as they are, they have a kind of charme as they are proof of the time when they were created. It anyway depends on which screen they are playing, my laptop look is of course not the same as the look on my TV.
I’m thinking about to buy the whole series from Amazon UK and might work on them as you have suggested but it’s a lot of work. Probably worth it, I love the serie so much, each actor and each (German) voice of them. In the German versions each episode is starting with a short version of “Paint it Black” from the Rolling Stones as well as my most beloved Band.
Attached is a screenshot with the data when the serie startet in Germany.