I did get to the end of the border, eventually, and then there was the small matter of sewing it on.
Surprisingly, it didn't seem half so long when I was sewing it on, that part seemed to go really quickly.
The border definitely gives all the bits their shape, and finally, it looks like a proper cardigan. Being black, and wool, over the months it's been in the making, it's managed to pick up a lot of threads, so now it's been washed. I shall block it, and it's ready to go, no buttons are needed for this one, so no delays.
There is a version of this with three quarter sleeves, which I may do, but it won't be in black.